External Memory Controller

ABSTRACT

A memory controller to provide memory access services in an adaptive computing engine is provided. The controller comprises: a network interface configured to receive a memory request from a programmable network; and a memory interface configured to access a memory to fulfill the memory request from the programmable network, wherein the memory interface receives and provides data for the memory request to the network interface, the network interface configured to send data to and receive data from the programmable network.

CLAIM OF PRIORITY

This application claims priority from U.S. Provisional PatentApplication No. 60/428,646, filed on Nov. 22, 2002; that is herebyincorporated by reference as if set forth in full in this applicationfor all purposes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to the following U.S. patent applications,each of which is hereby incorporated by reference as if set forth infull in this document for all purposes:

Ser. No. 09/815,122, entitled “Adaptive Integrated Circuitry withHeterogeneous and Reconfigurable Matrices of Diverse and AdaptiveComputational Units having Fixed, Application Specific ComputationalElements,” filed on Mar. 22, 2001;

Ser. No. 10/443,554, entitled “Uniform Interface for a Functional Nodein an Adaptive Computing Engine,” filed on May 21, 2003.

BACKGROUND OF THE INVENTION

The present invention is related in general to memory controllers andmore specifically to the design of a memory controller for use in anadaptive computing environment.

The advances made in the design and development of integrated circuits(“ICs”) have generally produced information-processing devices fallinginto one of several distinct types or categories having differentproperties and functions, such as microprocessors and digital signalprocessors (“DSPs”), application specific integrated circuits (“ASICs”),and field programmable gate arrays (“FPGAs”). Each of these differenttypes or categories of information-processing devices have distinctadvantages and disadvantages.

Microprocessors and DSPs, for example, typically provide a flexible,software-programmable solution for a wide variety of tasks. Theflexibility of these devices requires a large amount of instructiondecoding and processing, resulting in a comparatively small amount ofprocessing resources devoted to actual algorithmic operations.Consequently, microprocessors and DSPs require significant processingresources, in the form of clock speed or silicon area, and consumesignificantly more power compared with other types of devices.

ASICs, while having comparative advantages in power consumption andsize, use a fixed, “hard-wired” implementation of transistors toimplement one or a small group of highly specific tasks. ASICs typicallyperform these tasks quite effectively; however, ASICs are not readilychangeable, essentially requiring new masks and fabrication to realizeany modifications to the intended tasks.

FPGAs allow a degree of post-fabrication modification, enabling somedesign and programming flexibility. FPGAs are comprised of small,repeating arrays of identical logic devices surrounded by several levelsof programmable interconnects. Functions are implemented by configuringthe interconnects to connect the logic devices in particular sequencesand arrangements. Although FPGAs can be reconfigured after fabrication,the reconfiguring process is comparatively slow and is unsuitable formost real-time, immediate applications. Additionally, FPGAs are veryexpensive and very inefficient for implementation of particularfunctions. An algorithmic operation implemented on an FPGA may requireorders of magnitude more silicon area, processing time, and power thanits ASIC counterpart, particularly when the algorithm is a poor fit tothe FPGA's array of homogeneous logic devices.

An adaptive computing engine (ACE) or adaptable computing machine (ACM)allows a collection of hardware resources to be rapidly configured fordifferent tasks. Resources can include, e.g., processors, or nodes, forperforming arithmetic, logical and other functions. The nodes areprovided with an interconnection system that allows communication amongnodes and communication with resources such as memory, input/outputports, etc. One type of valuable processing is memory access services.In order to provide memory access services to access external memory, anexternal memory controller is typically needed.

Thus, there is a desire to provide a memory controller that providesmemory access services in an adaptive computing engine.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention generally relate to using a memorycontroller to provide memory access services in an adaptive computingengine.

In one embodiment, a memory controller in an adaptive computing engine(ACE) is provided. The controller includes a network interfaceconfigured to receive a memory request from a programmable network; anda memory interface configured to access a memory to fulfill the memoryrequest from the programmable network, wherein the memory interfacereceives and provides data for the memory request to the networkinterface, the network interface configured to send data to and receivedata from the programmable network.

In another embodiment, a memory controller includes a network interfaceconfigured to receive a memory request for a memory access service froma network; and one or more engines configured to receive the memoryrequest and to provide the memory access service associated with thememory request.

In yet another embodiment, a memory controller includes one or moreports configured to receive memory requests, wherein each port includesone or more parameters; an engine configured to receive a memory requestfrom a port in the one or more ports; and a data address generatorconfigured to generate a memory location for a memory based on the oneor more parameters associated with the port, wherein the engine isconfigured to perform a memory operation for the memory request usingthe generated memory location.

In another embodiment, a memory controller includes one or more portsconfigured to receive memory requests from requesting nodes, whereineach port includes one or more parameters, the one or more parametersconfigurable by information in the memory requests; a point-to-pointengine configured to receive a memory request from a port in the one ormore ports; a data address generator configured to generate a memorylocation for a memory based on the one or more parameters associatedwith the port, wherein the point-to-point engine performs a memoryoperation using the generated memory location while adhering to apoint-to-point protocol with the requesting node.

In another embodiment, a system for processing memory service requestsin an adaptable computing environment is provided. The system comprises:a memory; one or more nodes configured to generate a memory servicerequest; a memory controller configured to receive the memory servicerequest, the memory controller configured to service the memory servicerequest, wherein the memory controller reads or writes data from or tothe memory based on the memory service request.

A further understanding of the nature and the advantages of theinventions disclosed herein may be realized by reference of theremaining portions of the specification and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of an ACE device;

FIG. 2 shows a plurality of ACE devices, each having a plurality ofnodes, connected together in a development system;

FIG. 3 is a block diagram of a system for performing memory accessservices according to one embodiment of the present invention;

FIG. 4 illustrates a more detailed block diagram of memory controlleraccording to one embodiment of the present invention; and

FIG. 5 illustrates an embodiment of a point-to-point (PTP) engine usableto perform PTP memory services according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the invention uses an adaptive computingengine (ACE) architecture including an external memory controller (XMC)node. Details of an exemplary ACE architecture are disclosed in the U.S.patent application Ser. No. 09/815,122, entitled “Adaptive IntegratedCircuitry with Heterogeneous and Reconfigurable Matrices of Diverse andAdaptive Computational Units having Fixed, Application SpecificComputational Elements,” referenced, above.

In general, the ACE architecture includes a plurality of heterogeneouscomputational elements coupled together via a programmableinterconnection network. FIG. 1 illustrates an embodiment 100 of an ACEdevice. In this embodiment, the ACE device is realized on a singleintegrated circuit. A system bus interface 102 is provided forcommunication with external systems via an external system bus. Anetwork input interface 104 is provided to send and receive real-timedata. An external memory interface 106 is provided to enable the use ofadditional external memory devices, including SDRAM or flash memorydevices. A network output interface 108 is provided for optionallycommunicating with additional ACE devices, as discussed below withrespect to FIG. 2.

A plurality of heterogeneous computational elements (or nodes),including computing elements 120, 122, 124, and 126, comprise fixed anddiffering architectures corresponding to different algorithmicfunctions. Each node is specifically adapted to implement one of manydifferent categories or types of functions, such as internal memory,logic and bit-level functions, arithmetic functions, control functions,and input and output functions. The quantity of nodes of differing typesin an ACE device can vary according to the application requirements.

Because each node has a fixed architecture specifically adapted to itsintended function, nodes approach the algorithmic efficiency of ASICdevices. For example, a binary logical node may be especially suited forbit-manipulation operations such as, logical AND, OR, NOR, XORoperations, bit shifting, etc. An arithmetic node may be especially wellsuited for math operations such as addition, subtraction,multiplication, division, etc. Other types of nodes are possible thatcan be designed for optimal processing of specific types.

Programmable interconnection network 110 enables communication among aplurality of nodes such as 120, 122, 124 and 126, and interfaces 102,104, 106, and 108. The programmable interconnection network can be usedto reconfigure the ACE device for a variety of different tasks. Forexample, changing the configuration of the interconnections betweennodes can allow the same set of heterogeneous nodes to implementdifferent functions, such as linear or non-linear algorithmicoperations, finite state machine operations, memory operations,bit-level manipulations, fast-Fourier or discrete-cosinetransformations, and many other high level processing functions foradvanced computing, signal processing, and communications applications.

In one embodiment, programmable interconnection network 110 comprises anetwork root 130 and a plurality of crosspoint switches, includingswitches 132 and 134. In one embodiment, programmable interconnectionnetwork 110 is logically and/or physically arranged as a hierarchicaltree to maximize distribution efficiency. In this embodiment, a numberof nodes can be clustered together around a single crosspoint switch.The crosspoint switch is further connected with additional crosspointswitches, which facilitate communication between nodes in differentclusters. For example, cluster 112, which comprises nodes 120, 122, 124,and 126, is connected with crosspoint switch 132 to enable communicationwith the nodes of clusters 114, 116, and 118. Crosspoint switch isfurther connected with additional crosspoint switches, for examplecrosspoint switch 134 via network root 130, to enable communicationbetween any of the plurality of nodes in ACE device 100.

The programmable interconnection network (PIN) 110, in addition tofacilitating communications between nodes within ACE device 100, alsoenables communication with nodes within other ACE devices via networkinputs and outputs interfaces 104 and 108, respectively, and with othercomponents and resources through other interfaces such as 102 and 106.FIG. 2 shows a plurality of ACE devices 202, 204, 206, and 208, eachhaving a plurality of nodes, connected together in a development system200. The system bus interface of ACE device 202 communicates withexternal systems via an external system bus. Real-time input iscommunicated to and from ACE device 202 via a network input interface210. Real-time inputs and additional data generated by ACE device 202can be further communicated to ACE device 204 via network outputinterface 212 and network input interface 214. ACE device 204communicates real-time inputs and additional data generated by eitheritself or ACE device 202 to ACE device 206 via network output interface216. In this manner, any number of ACE devices may be coupled togetherto operate in parallel. Additionally, the network output interface 218of the last ACE device in the series, ACE device 208, communicatesreal-time data output and optionally forms a data feedback loop with ACEdevice 202 via multiplexer 220.

In accordance with embodiments of the present invention, a memorycontroller is used to provide memory access services in an ACEarchitecture. FIG. 3 is a high-level block diagram that illustrates thebasic concepts of a system 300 for performing memory access servicesaccording to one embodiment of the present invention. As shown, system300 includes PIN 110, nodes 301, a memory controller 302, and a memory304.

Nodes 301 can be any nodes, (e.g., computational elements or resources)in a computing device. Nodes 301 initiate memory service requests tomemory controller 302. For example, nodes 301 can initiate read andwrite commands. If a read command is initiated, the requesting node isconsidered a “consumer” in that it consumes data read from memory 304and if a write command is initiated, the requesting node is considered a“producer” in that it produces data to be written to memory 304. Theread and write commands may be in the form of different memory accessservices that are described below.

PIN 110 receives memory service requests from nodes 301 in the ACEdevice. Additionally, PIN 110 receives and/or sends data from/to memorycontroller 302 and receives and/or sends the data from/to the requestingnodes in the ACE device.

Memory controller 302 receives memory access service requests from PIN110 and processes the requests accordingly. In one embodiment, theservices provided by memory controller 302 include a peek and pokeservice, a memory random access (MRA) service, a direct memory access(DMA) service, a point-to-point (PTP) service, a real-time input (RTI)service and a message service. The peek and poke service allows arequesting node to peek (retrieve) data and poke (write) data found inmemory controller 302. A memory random access (MRA) service allows arequesting node to do a read and write to memory 304. A direct memoryaccess (DMA) service allows a requesting node to request large blocks ofdata from memory 304. A point-to-point (PTP) service allows a requestingnode to read and write data, and update port parameters, in a processthat conforms to a point-to-point protocol. In one embodiment, the PTPservice is used to read and write real-time streaming data. Thereal-time input (RTI) service performs the same service as to PTPservice but uses a reduced acknowledgement protocol. Additionally,memory controller 304 provides messaging to nodes in the ACE device. Forexample, memory controller 302 can provide confirmation acknowledgementmessages to requesting nodes that may be used for flow control.

In one embodiment, memory 304 is an external memory for an ACE device.Memory 304 receives memory service requests from memory controller 302and provides data to memory controller 302 when a read operation isrequested. Additionally, memory controller 302 may provide data tomemory 304 that is to be written to memory 304. Memory 304 may be anymemory, such as, a synchronous dynamic random access memory (SDRAM), aflash memory, static random access memory (SRAM) and the like.

The above-mentioned services that may be provided by memory controller302 will now be described. Although the following memory services aredescribed, it will be understood that a person skilled in the art willappreciate other memory services that memory controller 302 may provide.

Flow control is provided for a poke request in that a requesting pokewaits for a poke acknowledgement before initiating a new poke to thesame memory. In the case where multiple services are provided in memory304, multiple requests to different memories may be allowed.

FIG. 4 illustrates a more detailed block diagram of memory controller302 according to one embodiment of the present invention. As shown,memory controller 302 includes a PIN interface 400, one or more engines402, and a memory interface 404. Additionally memory 304 includes anSDRAM memory 406 and a flash memory 408.

PIN interface 400 is configured to receive memory service requests fromPIN 110. Additionally, PIN interface 400 is configured to send data orany other messages to PIN 110. In one embodiment, PIN interface 400includes a distributor, input arbiter, and an aggregator. Thedistributor and arbiter facilitate distributing data to one or moreengines 402. The aggregator aggregates words that will be sent to nodes.When a request is received at PIN interface 400, PIN interface 400determines which engine in engines 402 to send the reqUest to.

In one embodiment, PIN interface 400 also provides a priority system formemory service requests. For example, one memory priority system maygive a peek/poke memory service request the highest priority. Randomread requests that are received with a fast track or higher priorityindication are then given the next highest priority. All other requestsare given a lowest priority. For example, random memory access requestsare placed on a 132 entry first come first serve queue, DMA and PTPrequests are placed on a single 64 entry first come first serve queueand these two queues are serviced on a round robin basis.

As shown, one or more engines 402 includes a peek/poke engine 410, afast track engine 412, a random read/write engine 414, and a PTP/DMA/RTIengine 416 according to one embodiment of the invention. Although theseengines 402 are described, a person skilled in the art will appreciatethat other engines may be provided to perform functions related to thememory access services. Engines 402 process a memory service request andprovide the appropriate request to memory interface 404 to fulfill thememory service request. For example, engines 402 determine a memoryaddress that data should be read from in memory 304 or the data and amemory address in which data should be written to in memory 304. Theaction is then performed according to a protocol associated with thememory service request.

Memory interface 404 receives memory service requests from memoryinterface 404 and provides them to SDRAM memory 406 and/or flash memory408. Although SDRAM memory 406 and flash memory 408 are shown, it willbe understood that a person skilled in the art will appreciate othermemories that may be used.

The types of services that are provided by engines 402 will now bedescribed.

When a peek memory service request is received at PIN interface 400, itdetermines that the request should be sent to peek/poke engine 410. Thepeek request is received in one or more data words and PIN interface 400is configured to determine from data in the data words that a peekshould be performed. The peek request is then forwarded to peek/pokeengine 410, which determines peek address(es) that data should be readfrom. In one embodiment, peek requests are used to read data from memoryor registers found in controller 302. For example, registers storingparameters 422 in ports 418 may be peeked. The data request at thedetermined address(es) is then sent to appropriate registers. The datais then returned to peek/poke engine 410 and sent to the requesting nodethrough PIN interface 400 and PIN 110.

In order to provide flow control, the requesting node waits for receiptof prior peek data before initiating a new peek request to the samememory.

When a poke request is received at PIN interface 400, PIN interface 400determines that the request should be sent to peek/poke engine 410. Inone embodiment, a poke request is sent in one or more data words and PINinterface 400 determines from the one or more data words that therequest should be sent to peek/poke engine 410. Peek/poke engine 410receives a poke address word from the requester and a poke data word towrite to the address previously supplied by the poke address word. Forexample, registers including parameters 422 may have data written tothem. Peek/poke engine 410 also determines from the one or more datawords which register to write the data to.

After the data has been written, a poke acknowledgement may present bypeek/poke engine 410 to the requesting node through PIN 110 and PINinterface 400. Flow control can be realized by requiring a requestingnode to wait for full acknowledgement before initiating a new poke tothe same memory.

Fast track engine 412 is provided to perform memory access services thathave a higher priority. Thus, fast track engine 412 allows requestingnodes to send requests and data in an expedited manner.

When a memory random access read or write is received at PIN interface400, PIN interface 400 then provides the memory service request torandom read/write engine 414. In one embodiment, a double word (32-bits)on a double word boundary may be read at a certain specified address ora burst read, which reads 16 double words on double word boundaries, maybe performed.

In one embodiment, MRA read requests are placed in a queue and randomread/write engine 414 services requests in a first in/first outmethodology in one embodiment. When a request to memory 304 is ready,random read/write engine 414 sends the determined address with anindication of the appropriate memory that data should be read from tomemory interface 404. The request is forwarded to memory 304 and data isread and returned to random read/write engine 414. The data can then bereturned to the requesting node through PIN interface 400 and PIN 110.

In order to maintain flow control, in one embodiment, the requestingnode waits for receipt of prior MRA read data before initiating a newMRA read or write to the same memory. Thus, the requesting node may makea first read request to SDRAM memory 406 and a second request to flashmemory 408 simultaneously but cannot make multiple requests to SRAMmemory 406 or flash memory 408.

When PIN 400 receives a MRA write request, it determines from one ormore data words in the request that a MRA write should be performed. Forexample, a bit or any other indication may be set in the one or moredata words to indicate the request is a MRA request. The request is thenforwarded to random read/write engine 414, which determines a memorylocation from the one or more data words where the data should bewritten. The address is then stored in a table and when data for thewrite is received (either with the one or more data words containing therequest or in one or more data words received later), the data is thenstored in a temporary buffer. The MRA request is then placed in a queue.The queue is serviced in a first in/first out manner by randomread/write engine 414.

When the MRA write request is serviced, the data is retrieved from thetemporary buffer and written to the address included in the appropriateentry of the random address queue. In this case, the data, address, andwhich memory to write the data are sent to memory interface 404, whichwrites the data to either SDRAM memory 406 or flash memory 408 at theaddress specified. Random read/write engine 414 then sends a MRA writeacknowledgement to the requesting node. Flow control is maintainedbecause a requesting node waits for a MRA write acknowledgement beforeissuing a new random MRA read or write to the same memory.

A plurality of ports 418 are provided for the direct memory access(DMA), point-to-point (PTP), and real-time input (RTI) memory services.In one embodiment, each port includes DAG parameters and otherparameters 422 and a temporary buffer 424. In a preferred embodiment theDAG is used to generate sequences of addresses for both reading andwriting memory. For example, a node that desires to access a pattern ofmemory locations obtains the addresses from the DAG. The DAG can beconfigured in various ways such as, e.g., by a control node poking portconfiguration parameters. Another way to configure the DAG isdynamically via PTP control words. Details of the DAG are provided infollowing sections.

One or more DAG parameters 422 associated with a port 148 are used byDAG 420 to determine the appropriate data to retrieve from memory 304,or the appropriate location in memory to update. Other parameters can beincluded, such as temporary buffer parameters, control and statusregister bits, producer information, consumer information, counts, andthe like.

In one embodiment, each of ports 418 include a temporary buffer 424.Temporary buffer 424 is used to store one or more PTP/DMA/RTI words thatare received from a requesting node. When data is stored in temporarybuffer 424, an indication of what kind of request associated with thestored data is stored in queue 426.

A PTP_DMA_Queue 426 is maintained by thePTP/DMA/RTI engine 416 forservicing of ports. Various events as described below cause a port to beplaced on this first-in-first-out queue.

The services provided by PTP/DMA/RTI engine 416 will now be described.

Direct memory access services include a DMA read and a DMA writeservice. In a DMA read service, any of the ports 418 can serve as asource of a DMA channel set up by a requesting node 301. When a DMA readrequest for a port i in ports 418 is serviced, DAG 420 is configuredwith the DAG parameters for port i. Data is then read from memory 304,such as SDRAM memory 406 or flash memory 408, using the just configuredDAG 420 by PTP/DMA/RTI engine 416.

The DMA read may be for a large chunk of data and multiple reads may beneeded to read the entire requested chunk of data. Thus, memorycontroller 302 may send multiple chunks of data to a requesting node 301in response to a DMA read. In one embodiment, counts are used todetermine how much data to read. For example, chunks of data may be readin 32-bit words but the read request may be for seven bytes. The countwould be set to seven and when the first word, which includes fourbytes, is read, the count is decremented to three. When the next byte isread, the count is decremented to zero and only three bytes are readbecause the count was three. In some cases, multiple DMA reads may beserviced for a node.

In order to maintain flow control, memory controller 302 waits for a DMAread chunk acknowledgment from the requesting node before transmittingthe next chunk of data. Also, PTP/DMA/RTI engine 416 waits for a DMAdone message from the requesting node until a new DMA read from the samememory 304, such as SDRAM memory 406 or flash memory 408, is initiated.

PTP/DMA/RTI engine 416 can also perform a DMA write. Any of the ports inports 418 may serve as the destination of a DMA channel set up by arequesting node. Temporary buffer 424 is provided in each of ports 418in order to store incoming DMA data that is eventually written intomemory 304. Although buffer 424 is described, it will be understood thatbuffer 424 may not be used and the data may be streamed to PTP/DMA/RTIengine 416. Because a DMA write might be a write for large amounts ofdata, the data may arrive in multiple data words over a period of time.When a DMA write request is received at a port i in ports 418, if porti's temporary buffers 424 are already full, an error message is sent tothe requesting node. If not, the data is written sequentially into porti's temporary buffer 424 and a corresponding DMA write request is placedin queue 426. As more data is received on port i, the data is writtensequentially into the port's temporary buffer 424 if it is not alreadyfull. When the last data word for the DMA write request is received onport i, a DMA write request is placed in queue 426. Although the abovesequence is described, it will be understood that a person skilled inthe art will appreciate other ways of handling the received data.

When the DMA write request is ready to be serviced by PTP/DMA/RTI engine416, DAG 420 of PTP/DMA/RTI engine 416 is configured with DAG parameters422 for port i. Each successive DMA write request is read from queue 426and the corresponding data in port i's temporary buffer 424 is thenwritten to memory 304, such as SDRAM memory 406 or flash memory 408,using the just configured DAG 420. DAG 420 may calculate addresses basedon one or more parameters 422 associated with port I and an addressassociated with the applicable memory DMA request. The addresses may becalculated for each successive DMA write request and DAG 420 may beconfigured with parameters 422 for each write request.

In order to maintain flow control, the transmitting node waits for achunk acknowledgment from memory controller 302 that indicates the chunkof data has been stored in temporary buffer 424 before transmitting thenext chunk of data to be stored in port I's temporary buffer 424.Additionally, the requesting node waits for a DMA done message frommemory controller 302 before initiating a new DMA write to the samememory 304.

In one embodiment, counts are used to determine how much data to write.For example, chunks of data may be received in 32-bit words. The writerequest may be for seven bytes. The count would be set to seven and whenthe first word, which includes four bytes, is received and written, thecount is decremented to three. When the next word is received, the countis decremented to zero and only three bytes are written because thecount was three.

Point-to-point memory services may also be performed by PTP/DMA/RTIengine 416. Nodes 301 may read and write memory 304 and update selectedport parameters 422 via any of ports 418 using a point-to-pointprotocol. Memory controller 302 adheres to all point-to-pointconventions, performs forward and backward ACKing, and also maintainscounts for consumers and producers. Additionally, flow control ismaintained because of the point-to-point conventions. For example, in awrite request, neither temporary buffer 424 for ports 418 nor a bufferin memory 304 will overflow so long as the requesting node adheres toPTP conventions. Additionally, in a read request, memory controller 302will not overflow the consuming node's input buffer as long as therequesting node adheres to PTP conventions.

PTP/DMA/RTI engine 416 may perform point-to-point memory services usinga number of modes. For example, an auto-source mode provides an infinitesource of data. A read occurs automatically when there is availablespace in a consuming node's input buffer and read requests are not used.An infinite-sink mode may be provided to provide an infinite sink fordata. In this case, a write occurs when there is data in temporarybuffer 424 and new data overwrites old data when the main buffer isfull. In one embodiment, memory 304 includes a main buffer where data iswritten to. Thus, data is read from temporary buffer 424 and written tothe main buffer. Although a main buffer is described, it will beunderstood that data may be written to other structures in memory 304. Afinite-sink mode provides a finite sink for data. In this case, a writeoccurs when there is data in temporary buffer 424 and available space inthe main buffer and writing stops when the main buffer is full. A buffermode implements a first in/first out (FIFO) queue. In this case, writesfill the main buffer while reads drain the main buffer. A write occurswhen there is data in the temporary buffer and available space in themain buffer. A read occurs when there is sufficient data in the mainbuffer and available space in the consuming-nodes input buffer. A basicmode provides unrestricted writing to a data structure. In this case, awrite occurs when there is data in the temporary buffer, and old data inmemory is overwritten. Also, the basic mode provides unrestrictedreading of a data structure. A read occurs after an explicit readrequest is received and there is available space in the consuming nodesinput buffer.

FIG. 5 illustrates the general design of an engine such as PTP/DMA/RTIengine 416 of FIG. 4.

Data packets are received from a data source such as a distributor(e.g., from PIN Interface 400 of FIG. 4). The payload portion of eachincoming packet together with a bit indicating whether the payload is adata word or control word is stored in port temporary buffer 600. In apreferred embodiment, packets are 51 bits wide and can includedestination information, control information, parameter information,data, or a combination of these types of information. When a port isserviced, control words and data words are read from port temporarybuffer 600 and sent to control system 604 or unpacker 608, respectively.

Port parameters can be updated by information in “poke packets” or bycontrol-word information in incoming PTP/DMA packets. The parameterupdate information is provided to parameter control system 602. Portparameters are used to define characteristics of a port for specific ordesired functionality. For example, port parameters controlcharacteristics of temporary buffers, removing control and data wordsfrom the temporary buffer for processing, unpacking data (double-) wordsinto records in preparation for writing to main memory, writing andreading records to main memory, packing records read from memory intodouble-words and composing appropriate MIN words for transmission to theconsumer node, sending various control words—forward and backwardacknowledgements, DMA chunk acknowledgements and DMA Done messages—tothe producer and consumer nodes; and other functions.

Unpacked data produced by unpacker 608 can include one or more records.Each record can be 8, 16 or 32 bits. A 4-bit byte select is sent witheach 32-bit unpacked datum to indicate which of the bytes contain validdata and are to be written to memory.

Control words are used to specify parameters and other controlinformation and are discussed in detail in the sections, below. Forexample, a control word can include information that indicates whether aparameter update is to be followed by a read using the updated portparameters.

Data address generator 606 is used to generate an address, or addresses,for use in reading from or writing to memory. The data address generatoris configured by the DAG parameters included in the port parameters 602.Packer 612 is used to pack records received from memory into 32-bit datawords for transmission to the consuming node. Packet assembly 610 isused to assemble the 32-bit data words into a standard PTP, DMA or RTIpackets for transmission to the consuming node.

In a preferred embodiment, the XMC node adheres to the same networkprotocol conventions as other nodes in the ACE. Examples of ACE networkprotocols in the preferred embodiment include Peek/Poke, MRA, PTP, DMA,RTI, message, etc. This allows XMC nodes to benefit from the samescaling features and adaptable architecture of the overall system.Details of a network protocol used in the preferred embodiment can befound in the related patent application entitled “Uniform Interface fora Functional Node in an Adaptive Computing Engine,” referenced above.

In a preferred embodiment of the XMC there are 64 ports—each one acombination input/output port. Three matrix interconnect network (MIN)(also referred to as the programmable interconnect network (PIN))protocols—Direct-Memory-Access (DMA), Point-To-Point (PTP) andReal-Time-Input (RTI)—make use of these ports for both writing data toand reading data from memory.

Memory addresses for both writing and reading are generated by a logicalDAG associated with each port. This logical DAG is actually a set of DAGparameters that are used to configure a single physical DAG, as needed,for memory writes and reads.

Each port also has a temporary buffer to temporarily store incomingPTP/RTI/DMA words from the MIN. The total size of all 64 temporarybuffers is 16 Kbytes arranged as 4K×33 bit words. The 33rd bit of eachword indicates whether a double-word is a data word or a control word,as described below.

Each XMC port is associated with a set of parameters that define thecharacteristics of that port. These parameters configure the XMChardware when a port is called upon to perform one of the followingtasks:

Writing incoming control and data words into the temporary buffer;

Removing control and data words from the temporary buffer forprocessing;

Unpacking data (double-) words into records in preparation for writingto main memory;

Writing records to main memory;

Reading records from main memory;

Packing records read from memory into double-words and composingappropriate MIN words for transmission to the consumer node; and

Sending various control words—forward and backward acknowledgements, DMAchunk acknowledgements and DMA Done messages—to the producer andconsumer nodes.

The value of each port parameter can be either static or dynamic. Ifstatic, then the parameter is updated only by a poke from the K-Node. Ifdynamic, then the parameter can be updated by a poke from the K-Node andalso during normal XMC operation.

The Control and Status Bits described in Table A are the Parameters thatdirect the behavior of ports and define their mode of operation.

TABLE A Control and Status Bit parameters Parameter DescriptionPort_Enabled 0: Port disabled (Static Value) 1: Port enabledPort_Type[1:0] 00: PTP (Static Value) 01: PTP_Packet_Mode 10: RTI 11:DMA Record_Size[1:0] 00: Byte (8-bit) (Static Value) 01: Word (16-bit)10: Double-Word (32-bit) DAG_Address_Mode[1:0] 00: 1-D (Static Value)01: 2-D 10: Bit_Reverse Auto_Read 0: Port does not support automaticreads (Static Value) 1: Producer/Consumer counts can automaticallytrigger a read 0: Consumer_Count not checked in auto read Buffer_Read 0:Consumer_Count not checked in auto read (Static Value) 1:Consumer_Count >= 0 for auto read Buffer_Write 0: New data overwritesold data in memory (Static Value) 1: No writes to main-memory bufferwhen full Update_Index 0: Update DAG_X_Index and DAG_Y_Index only by wayof poke (Static Value) 1: Update DAG_X_Index and DAG_Y_Index after eachDAG use New_MIN_Word_On_YWrap 0: Ignore DAG_Y_Index wrap whenunpacking/packing MIN words (Static Value) 1: Start unpacking/packingnew MIN word when DAG_Y_Index wraps High_Speed_Write 0: Normal mode—porthandles all incoming words (Static Value) 1: High-speed mode—port doesnot support read requests Burst 0: Normal DAG-addressing mode (StaticValue) 1: High-throughput mode for accessing contiguous blocks of 2-Ddata Random_Access 0: Normal DAG addressing when performing read request(Static Value) 1: DAG addressing bypassed when performing read request

The two DMA Bits in Table B are used to control DMA transfers from andto the XMC respectively:

TABLE B DMA Bits Parameter Description DMA_Go Poking this bit with a 1initiates a (Static Value) DMA transfer from the XMC to ConsumerDMA_Write_Last_Word 0: DMA_Write_Last_Word_Of_Chunk (Dynamic Value)initiated DMA service request 1: DMA_Write_Last_Word initiated DMAservice request

The DAG parameters in Table C—together with DAG_Address_Mode—determinethe sequence of addresses generated by the port's Data AddressGenerator. See section 3.2 for more details.

TABLE C DAG Parameters DAG_Origin[27:0] Unsigned integer; Units = bytes;Base address of block (Dynamic Value) 1-D mode read: DAG Address =DAG_Origin + DAG_X_Index 1-D mode write: DAG Address = DAG_Origin +DAG_Y_Index 2-D mode: DAG Address = DAG_Origin + DAG_X_Index +DAG_Y_Index Bit_Reverse mode read or write: DAG Address = DAG_Origin +reverse(DAG_X_Index)† Must be on a Dword boundary, i.e. [1:0] = 00;†reverse(b, p0, p1) - reverse bits from bitpos p0 thru bitpos p1, e.g.:for (i = 0; i <=(p1−p0−1)/2; i++) { swap(b[p0+i], b[p1−i]); }DAG_X_Index[27:0] Unsigned integer; Units = bytes (Dynamic Value)Initial value must be less than DAG_X_Limit. 1-D mode, after a read, or2-D mode, after a read or write: DAG_X_Index += DAG_X_Stride Bit_Reversemode, after a read or write: DAG_X_Index += 1, 2, or 4 (byte, word,dword record, respectively) Then test:  if DAG_X_Index ≧ DAG_X_Limit (+XWrap)   DAG_X_Index −= DAG_X_Limit  else if DAG_X_Index < 0 (−X Wrap)  DAG_X_Index += DAG_X_Limit DAG_X_Stride[27:0] Signed integer; Units =bytes (Dynamic Value) Absolute value must be less than DAG_X_Limit. 1-D,2-D mode: Increment/decrement to DAG_X_Index Bit_Reverse mode:reverse(1) = 2{circumflex over ( )}(n − 1), i.e. a single bit markingthe leftmost bit position to be reversed in DAG_X_Index DAG_X_Limit[27:0] Unsigned integer; Units = bytes (Dynamic Value) 1-D mode read -block size 1-D mode write - not used 2-D mode read or write - X blocksize Bit_Reverse mode - block size DAG_Y_Index[27:0] Unsigned integer;Units = bytes (Dynamic Value) Initial value must be less thanDAG_Y_Limit. 1-D mode, after a write, or 2-D mode, after an X Wrap:DAG_Y_Index += DAG_Y_Stride Bit_Reverse mode - not used Then test:  ifDAG_Y_Index ≧ DAG_Y_Limit (+Y Wrap)   DAG_Y_Index −= DAG_Y_Limit  elseif DAG_Y_Index < 0 (−Y Wrap)   DAG_Y_Index += DAG_Y_LimitDAG_Y_Stride[27:0] Signed integer; Units = bytes (Dynamic Value)Absolute value must be less than DAG_Y_Limit 1-D, 2-D mode:Increment/decrement to DAG_Y_Index Bit_Reverse mode - not usedDAG_Y_Limit[27:0] Unsigned integer; Units = bytes (Dynamic Value) 1-Dmode read - not used 1-D mode write - block size 2-D mode read orwrite - Y block size Bit_Reverse mode - not used

The Temporary-Buffer Parameters in Table D define the size of temporarybuffer of a port and provide the write-pointer and read-pointer neededto implement a circular first-in-first-out queue.

TABLE D Temporary-Buffer Parameters Parameter DescriptionBuffer_Size[3:0] 0000: 4 (bytes) (Static Value) 0001: 8 0010: 16 0011:32 0100: 64 0101: 128 0110: 256 0111: 512 1000: 1024 1001: 2048 1010:4096 1011: 8192 1100: 16384 Write_Address[11:0] Write pointer (DynamicValue) Read_Address[11:0] Read pointer (Dynamic Value)

The Producer/Consumer Information in Table E is used in various fieldsin the MIN words that are sent to the Data Producer, Control Producerand Consumer.

TABLE E Producer/Consumer Information Parameter DescriptionData_Producer_ID[7:0] Address of Data Producer (Static Value) (Thesource of PTP/DMA data words) Data_Producer_Mode Mode bit of DataProducer (Static Value) Data_Producer_Port[5:0] Port number of DataProducer (Static Value) Data_Producer_Task[4:0] Task number of DataProducer (Static Value) Control_Producer_ID[7:0] Address of ControlProducer (Static Value) (The source of PTP control words)Control_Producer_Mode Mode bit of Control Producer (Static Value)Control_Producer_Port[5:0] Port number of Control Producer (StaticValue) Control_Producer_Task[4:0] Task number of Control Producer(Static Value) Consumer_ID[7:0] Address of Consumer (Static Value) (Thedestination of read data) Consumer_Mode Mode bit of Consumer (StaticValue) Consumer_Port[5:0] Port number of Consumer (Static Value)Consumer_Task[4:0] Task number of Consumer (Static Value)

The Counts in Table F provide flow control between (a) the Data andControl Producers and the XMC, (b) the temporary buffer and themain-memory buffer (when Buffer_Write=1) and (c) the XMC and theConsumer.

TABLE F Counts Parameter Description ACK_Count[13:0] A signed numberindicating the number of bytes in a port's (Dynamic Value) temporarybuffer minus 1; A port is serviced when ACK_Count ≧ 0 Initialized atsystem reset to −1 indicating that the temporary buffer is empty; andthen incremented in response to forward ACKs from the Data and ControlProducers indicating the number of data/control words, expressed inbytes, placed in the temporary buffer; and then decremented when the XMCsends backward ACKs to the Data Producer and Control Producer indicatingthe number of data words and control words, respectively - expressed inbytes - removed from the temporary buffer Read_Count[13:0] An unsignednumber indicating the number of records read (Static Value) from memoryand sent to the consumer node per read-request or auto-readProducer_Count[13:0] A signed number reflecting the available space, inbytes, in the (Dynamic Value) Consumer's input-buffer; Producer_Count <0 indicates that the consumer node input-buffer has available space forRead_Count records Should be initialized to RC − CBS − 1 (a negativevalue), where RC is Read_Count, expressed in bytes, and CBS is theConsumer's input-buffer size, in bytes; Incremented when the XMC sendsforward ACKs to the Consumer indicating the amount of data, in bytes,read from memory and sent to the Consumer; and then decremented inresponse to backward ACKs from the Consumer indicating the amount ofspace, in bytes, freed up in the Consumer's input bufferConsumer_Count[27:0] A signed number reflecting the number of bytes inthe main- (Dynamic Value) memory buffer; Consumer_Count ≧ 0 indicatesthat the main-memory buffer has at least Read_Count records; Applicableonly when Buffer_Read = 1 Should be initialized to a (negative) valuebetween TBS − MBS and −RC, where TBS is the temporary-buffer size, inbytes, MBS is the main-memory-buffer size, in bytes, and RC isRead_Count, expressed in bytes; Incremented when the XMC moves data fromthe temporary buffer to the main- memory buffer; and then decrementedwhen the XMC sends forward ACKs to the Consumer indicating the amount ofdata, in bytes, read from the main-memory buffer and sent to theConsumer Buffer_Full_Offset[27:0] A signed number which, when added toConsumer_Count, (Static Value) indicates XMC buffer status;Consumer_Count + Buffer_Full_Offset ≧ 0 indicates that the main- memorybuffer is full; The main-memory buffer is considered to be full when itdoes not have at least a temporary-buffer's worth of available space;Applicable only when Buffer_Write = 1 Should be initialized to TBS − MBS− ICC − 1 where TBS is the temporary-buffer size, in bytes, MBS is themain-memory- buffer size, in bytes, and ICC is the initial value ofConsumer_Count

Table C, above, describes XMC DAG parameters. The 3 accessing modes(1-D, 2-D, and Bit_Reverse) are explained below. Special cases are alsodiscussed relating to Y-Wrap and Burst Mode.

The DAG includes the ability to generate patterned addresses to memory.Three parameters—Index, Stride, and Limit—in each of X and Y definethese patterns. In the simplest 1-dimensional case, the Index parameteris incremented by Stride, tested against the block size given by Limit,and then added to Origin to determine the final address.

Note that Stride is a signed quantity, and can be negative to enablestepping backwards through a block of memory addresses. If the Index isincremented/decremented outside the block (0 thru Limit-1), the Limit issubtracted/added respectively to bring the address back within theblock. In this way, circular buffers with automatic wrap-aroundaddressing are easily implemented. In general, any type of addressing,address incrementing/decrementing, indexing, etc., can be used with DAGsof different designs.

In a 1-D addressing mode, the DAG writes or reads addresses in a linearfashion. On each advance, DAG_X_Stride is added to DAG_X_Index, and theresult tested greater than or equal to DAG_X_Limit and less than 0(since DAG_X_Stride can be negative). In these cases, DAG_X_Index isdecremented or incremented, respectively, by DAG_X_Limit, thus restoringit to the proper range.

When in 1-D Write Mode, only, the DAG uses the DAG_Y_Index,DAG_Y_Stride, and DAG_Y_Limit parameters, not X, to compute the writeaddress. This is so that read operations can be performed concurrently,using the X parameters in the usual way, to create a circular buffersuch as a FIFO.

In a 2-D addressing mode, the DAG writes or reads addresses in2-dimensional “scan-line” order, utilizing both the X and Y parameterssimilarly to the 1-D mode. X advance is performed first, and an X Wrap(either + or −) causes a Y advance (and thus a potential Y Wrap aswell). See the DAG advance pseudo-code description in section 3.2.4below.

Note that Y parameters are always specified in units of bytes, not scanlines or data items.

Bit-reversed addressing is included in the hardware to enableimplementation of Fast Fourier Transforms and other interleaved or“butterfly” computations. In this mode, bits within the DAG_X_Indexfield are reversed (swapped) just prior to using them in the memoryaddress computation.

In Bit_Reverse mode, DAG_X_Stride is not used as an increment, butinstead determines the range of bits to reverse within DAG_X_Index.Specifically, the DAG_X_Stride should be set to reverse(1)=2̂(n−1)=½ thesize of the block in bytes. Bits p through n−1 will be reversed in theDAG_X_Index, where p=0, 1, 2 for Record_Size of byte, word, and dword,respectively.

Example: For a 2̂12=4096-point FFT in byte mode, parameters might be

DAG_X_Index=0x0, DAG_X_Stride=0x800, DAG_X_Limit=0x1000.

Thus the hardware will reverse bits 0-11, and the address sequence is

address reverse(address, 0, 11) 0 0x000 1 0x800 2 0x400 3 0xc00 4 0x2005 0xa00 . . . . . .

As in other modes, the resulting reversed DAG_X_Index value is added tothe Origin address before being used to access memory.

In Bit_Reverse mode, note that the starting DAG_X_Index, theDAG_X_Limit, and the Origin are byte addresses specified normally—NOTbit-reversed. However, in this mode, the Origin must be on a double-wordboundary, i.e. bits [1:0]=00;

Although the X Wrap mechanism works in Bit_Reverse mode, typicallyDAG_X_Index is initialized to 0 and a single array of 2̂n values will beaddressed once.

Combining the above parameter definitions, the calculation of the DAGmemory addresses is as follows:

When the DAG is advanced:

-   -   If Address_Mode=1-D and the DAG is generating a Read Address [or        Bit_Reverse mode]:        -   DAG_X_Index=DAG_X_Index+DAG_X_Stride [+1, 2, or 4 instead if            Bit_Reverse mode]        -   If DAG_X_Index>=DAG_X_Limit, (+X wrap)            -   DAG_X_Index=DAG_X_Index−DAG_X_Limit;        -   Else if DAG_X_Index<0, (−X wrap)            -   DAG_X_Index=DAG_X_Index+DAG_X_Limit;        -   Memory Address=Origin+DAG_X_Index [+reverse(DAG_X_Index)            instead if Bit_Reverse mode]    -   If Address_Mode=1-D and the DAG is generating a Write Address:        -   DAG_Y_Index=DAG_Y_Index+DAG_Y_Stride        -   If DAG_Y_Index>=DAG_Y_Limit, (+Y wrap)        -   DAG_Y_Index=DAG_Y_Index−DAG_Y_Limit;        -   Else if DAG_Y_Index<0, (−Y wrap)            -   DAG_Y_Index=DAG_Y_Index+DAG_Y_Limit;        -   Memory Address=Origin+DAG_Y_Index;    -   If Address_Mode=2-D:        -   DAG_X_Index=DAG_X_Index+DAG_X_Stride;        -   If DAG_X_Index>=DAG_X_Limit, (+X wrap)            -   DAG_X_Index=DAG_X_Index−DAG_X_Limit;            -   DAG_Y_Index=DAG_Y_Index+DAG_Y_Stride;            -   If DAG_Y_Index>=DAG_Y_Limit, (+Y wrap)                -   DAG_Y_Index=DAG_Y_Index−DAG_Y_Limit;        -   Else if DAG_Y_Index<0, (−Y wrap)            -   DAG_Y_Index=DAG_Y_Index+DAG_Y_Limit;        -   Else if DAG_X_Index<0, (−X wrap)            -   DAG_X_Index=DAG_X_Index+DAG_X_Limit;            -   DAG_Y_Index=DAG_Y_Index+DAG_Y_Stride;            -   If DAG_Y_Index>=DAG_Y_Limit, (+Y wrap)                -   DAG_Y_Index=DAG_Y_Index−DAG_Y_Limit;            -   Else if DAG_Y_Index<0, (−Y wrap)                -   DAG_Y_Index=DAG_Y_Index+DAG_Y_Limit;        -   Memory Address=Origin+DAG_X_Index+DAG_Y_Index

Tables G-N, below, shows “for loop” representations in C pseudo-code ofvarious DAG addressing modes. Capitalized names such as Origin, Index,Stride, Limit, etc. represent the corresponding DAG parameters. Theexamples below all assume Record_Size=Dword=4 bytes, and positivestrides. Note that DAG parameters are always given in units of bytes,not records.

TABLE G Linear Addressing Definiti n // Linear addressing voidDAG_Linear ( byte *Origin, uint28 Index, int28 Stride, uint28 Limit,int28 count) { // count < Limit int28 i; for (i=Index; i<Index+count;i+=Stride) { printf(“%d: %d %d\n”, i, Origin+i, (dword)Origin[i]); } }

TABLE H Linear Addressing Example Given the following memory contents,address contents 0x22bee8 7 0x22bee4 6 0x22bee0 5 0x22bedc 4 0x22bed8 30x22bed4 2 0x22bed0 1 0x22becc 0 the function call  DAG_Linear(0x22bed0,0, 1*4, 20*4, 6); yields iteration address contents 0: 0x22bed0 1 1:0x22bed4 2 2: 0x22bed8 3 3: 0x22bedc 4 4: 0x22bee0 5 5: 0x22bee4 6

TABLE I Circular Addressing Definiti n // Circular (wraparound)addressing void DAG_Circular_1D( byte *Origin, uint28 Index, int28Stride, uint28 Limit, int28 count) { int28 i, imod; for (i=Index;i<Index+count; i+=Stride) { imod = i % Limit; printf(“%d: %d %d\n”, i,Origin+imod, (dword)Origin[imod]); } }

TABLE J Circular Addressing Example Given the following memory contents,address contents 0x22bee8 7 0x22bee4 6 0x22bee0 5 0x22bedc 4 0x22bed8 30x22bed4 2 0x22bed0 1 0x22becc 0 the function call DAG_Circular_1D(0x22bed0, 0, 1*4, 6*4, 10); yields iteration addresscontents 0: 0x22bed0 1 1: 0x22bed4 2 2: 0x22bed8 3 3: 0x22bedc 4 4:0x22bee0 5 5: 0x22bee4 6 6: 0x22bed0 1 7: 0x22bed4 2 8: 0x22bed8 3 9:0x22bee0 4

TABLE K 2D Addressing Definition // 2-D Addressing void DAG_2D( byte*Origin, uint28 xIndex, int28 xStride, uint28 xLimit, uint28 yIndex,int28 yStride, uint28 yLimit) { int28 x, y; // Access a one-dimensionalarray through two loops (2-D) for (y=yIndex; y<yIndex+yLimit;y+=yStride) { for (x=xIndex; x<xIndex+xLimit; x+=xStride) { printf(“%d%d: $d %d\n”, x, y, Origin+x+y, (dword)Origin[x+y]); } } }

TABLE L 2D Addressing Example Given the following memory contents (a 2-Dimage, X × Y = 3 columns × 3 rows embedded in 5 columns × 4 rows),address contents 0x22bf18 9 0x22bf14 8 0x22bf10 7 0x22bf0c 6 0x22bf08 50x22bf04 4 0x22bf00 3 0x22befc 2 0x22bef8 1 0x22bef4 0 0x22bf40 190x22bf3c 18 0x22bf38 17 0x22bf34 16 0x22bf30 15 0x22bf2c 14 0x22bf28 130x22bf24 12 0x22bf20 11 0x22bf1c 10 the function call  DAG_2D(0x22bef8,0, 1*4, 3*4, 0, 5*4, 15*4); yields x y address contents 0  0: 0x22bef8 14  0: 0x22befc 2 8  0: 0x22bf00 3 0 20: 0x22bf0c 6 4 20: 0x22bf10 7 820: 0x22bf14 8 0 40: 0x22bf20 11 4 40: 0x22bf24 12 8 40: 0x22bf28 13

TABLE M Bit-Reverse Addressing Definition // Bit-Reverse addressing(with wraparound) void DAG_BitReverse( byte *Origin, uint28 Index, int28Stride, uint28 Limit, int28 count) { int28 i, irev; for (i=Index;i<Index+count*4; i+=4) {// inc by 4 for dwords irev = Bit_Rev(i %Limit); // swap bits 2 thru Stride bit printf(“%d: %d $d\n”, i,Origin+irev, (dword)Origin[irev]); } }

TABLE N Bit-Reverse Addressing Example Given the following memorycontents (an 8-element block), address contents 0x22bef0 9 0x22beec 80x22bee8 7 0x22bee4 6 0x22bee0 5 0x22bedc 4 0x22bed8 3 0x22bed4 20x22bed0 1 0x22becc 0 the function call  DAG_BitReverse(0x22bed0, 0,4*4, 8*4, 12); // Stride = 2{circumflex over ( )}(n−1) = 4 yieldsiteration address contents  0: 0x22bed0 1  4: 0x22bee0 5  8: 0x22bed8 312: 0x22bee8 7 16: 0x22bed4 2 20: 0x22bee4 6 24: 0x22bedc 4 28: 0x22beec8 32: 0x22bed0 1 36: 0x22bee0 5 40: 0x22bed8 3 44: 0x22bee8 7

Any of the 64 PTP/DMA ports can serve as the source of a DMA channel setup by the K-Node/Host. In a preferred embodiment, only one DMA channelto/from memory at a time can be supported.

Actions

When Status_Register[i].DMA_Go is poked with a 1,

-   -   1) Place a Service Request for Port i in the PTP_DMA_Queue if        one is not already pending

When a Service Request for Port i is serviced withControl_Register[i].Port_Type=DMA and Register[i].DMA_Go=1:

-   -   1) Pop Port i from the PTP_DMA_Queue    -   2) If Status_Register[i].Port_Enabled=0 a) Send a Port Disable        Acknowledgement to the K-Node        -   b) Terminate servicing of Port i    -   3) Load Port-i DAG parameters into corresponding DAG registers    -   4) Note: When DAG_Address_Mode[i]=1-D, the DAG uses the three X        registers for reading and the three Y registers for writing    -   5) Read Read_Count [i] records from main memory under DAG        direction, pack them from right to left^(†) into double-words        and send to Consumer[i] via a sequence of DMA Read Data's        followed by a single DMA Read Last Word.

Flow Control

The K-Node waits for a DMA Done message from the destination node beforeinitiating a new DMA read/write from/to the same memory.

Direct-Memory-Access Write

Any of the PTP/DMA 64 ports can serve as the destination of a DMAchannel set up by the K-Node/Host.

Actions

When a DMA Write from the MIN is received on Port i:

-   -   1) Place the 32-bit payload, together with a bit indicating that        the double-word is a data word, sequentially into Port i's        (33-bit-wide, circular) temporary buffer.    -   2) Increment Ack_Count[i] by 4.

When a DMA Write Last Word Of Chunk from the MIN is received on Port is

-   -   1) Perform DMA Write actions.    -   2) Set Status_Register[i].DMA_Write_LastWord to 0.    -   3) Place a Service Request for Port i in the PTP_DMA_Queue if        one is not already pending.

When a DMA Write Last Word from the MIN is received on Port i:

-   -   1) Perform DMA Write actions.    -   2) Set Status_Register[i].DMA_Write_Last_Word to 1.    -   3) Place a Service Request for Port i in the PTP_DMA_Queue if        one is not already pending.

When a Service Request for DMA-Port i is serviced

-   -   1) Pop Port i from the PTP_DMA_Queue    -   2) If Status_Register[i].Port_Enabled=0        -   a) Send a Port Disable Acknowledgement to the K-Node        -   b) Terminate servicing of Port i    -   3) Load Port-i DAG parameters into corresponding DAG registers    -   4) Note: When DAG_Address_Mode[i]=1-D, the DAG uses the three X        registers for reading and the three Y registers for writing    -   5) Initialize signed-integer C to Ack_Count[i]/4    -   6) While C>=0:        -   a) Decrement C by 1        -   b) Remove double-word from temporary buffer        -   c) Unpack double-word from right to left^(†) and write            records to memory under DAG direction.    -   7) Decrement Ack_Count[i] by 4 times the total number of        double-words removed from Port i's temporary buffer    -   8) If Status_Register[i].DMA_Write_Last_Word=0, send a DMA Chunk        Acknowledgement to Data_Producer[i]; Omit if no records were        written to memory    -   9) Else if Status_Register[i].DMA_Write_Last_Word=1, send a DMA        Done message to the K-Node; Omit if no records were written to        memory    -   10) If Update_Index[i]=1:        -   a) Update X_Index[i] DAG parameter with X_Index DAG register        -   b) Update Y_Index[i] DAG parameter with Y_Index DAG register            ^(†) Records are packed and unpacked from right to left            because the XMC is little endian.

The DMA source waits for a DMA Chunk Acknowledgement from the memorycontroller before transmitting the next chunk (chunk size must be lessthan or equal to the size_of the port's temporary buffer).

The K-Node waits for DMA Done message from the memory controller beforeinitiating a new DMA read/write from/to the same memory.

Nodes may read and write memory and update selected port parameters viaany of the 64 ports of the memory controller using the point-to-pointprotocol. The memory controller performs forward and backward ACKing andmaintains Consumer Counts and Producer Counts.

The memory controller recognizes a data word where the payload fieldcontains data to be written to memory and a control word where thepayload field contains port-update information and a bit indicatingwhether the update is to be followed by a read using the DAG. When theupdate is followed by a read request the control word is called a ReadRequest. Table I, below, shows different types of control words. PTPdata words and PTP control words may be sent to a memory Port in anyorder and are processed in the order received.

TABLE I PTP Control-Word Fields Field Description Payload[27:0] NewParameter Value Payload[30:28] 000: Update DAG_Origin 001: UpdateDAG_X_Index 010: Update DAG_X_Stride 011: Update DAG_X_Limit 100: UpdateDAG_Y_Index 101: Update DAG_Y_Stride 110: Update DAG_Y_Limit 111: UpdateRead_Count Payload[31] 0: No Read Request 1: Read Request

Generally, data words and control words sent to the XMC are generatedindependently by separate tasks running on separate nodes. Therefore,when the XMC sends acknowledgements to the nodes to indicate that acontrol word or other message or information has been received, the XMCmust send separate acknowledgments, with appropriate values, to the taskor node that is producing data words. The task or node that is producingthe data word is referred to as the “Data Producer”. A task or node thatis producing control words is referred to as the “Control Producer.” TheXMC maintains information on the Data Producer and Control Producer inorder to properly send backward acknowledgements to both.

In general, tasks or nodes can be referred to as a “process” or as acomponent that performs processing. Although specific reference may bemade to hardware or software components, it should be apparent thatfunctions described herein may be performed by hardware, software or acombination of hardware and software.

In a preferred embodiment, all words—both data and control—arriving at aPTP/RTI port on the XMC are placed sequentially into the same temporarybuffer. For a case where two types of words are generated independently,typically by different nodes, it is necessary to allocate a portion ofthe temporary buffer to data words and a portion to control words toprevent buffer overflow.

When a PTP Write, PTP Packet-Mode Write or RTI Write from the MIN isreceived on Port i the following actions are performed:

-   -   1) Place the 32-bit payload, together with a bit indicating        whether the word is a data word or control word, sequentially        into Port i's (33-bit-wide, circular) temporary buffer.    -   When a Forward Acknowledgement from the MIN is received on Port        i:    -   1) Increment Ack_Count[i] by Ack Value (which is positive)        (Note: Forward Acknowledgement's from the Data_Producer and the        Control_Producer are treated identically.)    -   2) Place a Service Request for Port i in the PTP_DMA_Queue if        one is not already pending    -   When a Backward Acknowledgement from the MIN is received on Port        i,    -   1) Increment Producer_Count[i] by Ack Value (which is negative)    -   2) If the sign bit of Producer_Count[i] is now a 1        (Producer_Count[i] is negative), place a Service Request for        Port i in the PTP_DMA_Queue if one is not already pending    -   When a Service Request for PTP/RTI-Port i is serviced:    -   1) Pop Port i from the PTP_DMA_Queue    -   2) If Status_Register[i].Port_Enabled=0    -   a) Send a Port Disable Acknowledgement to the K-Node        -   b) Terminate servicing of Port i    -   3) Load Port-i DAG parameters into corresponding DAG registers    -   4) Note: When DAG_Address Mode[i]=1-D, the DAG uses the three X        registers for reading and the three Y registers for writing    -   5) If ((Control_Register[i].Write_Port=1) OR        (Producer_Count[i]<0)) AND        -   (Control_Register[i].Buffer_Write=0) OR the main buffer is            NOT full)    -   a) Initialize signed-integer C to Ack_Count[i]/4    -   b) While C>=0:    -   i) Decrement C by 1    -   ii) Remove double-word from temporary buffer    -   iii) If the double-word is a data word:    -   (1) Unpack data word from right to left^(†) and write records to        memory under DAG direction.    -   iv) Else (if the double-word is a control word):    -   (1) Update indicated DAG Parameter    -   (2) If a read is indicated    -   (a) Read Read_Count [1] records from memory under DAG direction,        pack them from right to left into double-words and send to        Consumer[i] via a sequence of PTP Read Data's    -   (b) Break from While loop    -   c) Decrement Ack_Count[i] by 4 times the total number of data        and control double-words removed from Port i's temporary buffer    -   6) Increment Consumer_Count[i] by 4 times the total number of        data double-words removed from the Port i's temporary buffer and        written to memory    -   7) Send a Backward Acknowledgement to Data_Producer[i] with an

ACK value equal to minus 4 times the number of data words removed fromPort i's temporary buffer; Omit if Control_Register[i].Port_Type=RTI orif no data words were consumed

-   -   8) Send a Backward Acknowledgement to Control_Producer[i] with        an ACK value equal to minus 4 times the number of control words        removed from Port i's temporary buffer; Omit if no control words        were consumed    -   9) If Control_Register[i].Auto_Read=1 AND Producer_Count[i]<0        AND (Control_Register[i].Buffer_Read=0 OR Consumer_Count[i]>=0)    -   a) Read Read_Count [i] records from memory under DAG direction,        pack them from right to left into double-words and send to        Consumer[i] via a sequence of PTP Read Data's    -   10) Increment Producer_Count[i] by 4 times the total number of        double-words sent to Consumer[i] (via read requests and auto        reads)    -   11) Decrement Consumer_Count[i] by 4 times the total number of        double-words sent to Consumer[i] (via read requests and auto        reads)    -   12) Send a Forward Acknowledgement to Consumer[i] with an ACK        value equal to 4 times the number of double-words sent to        Consumer[i] (via read requests and auto reads); Omit if no words        were sent to Consumer[i]    -   13) If Update_Index[i]=1:    -   a) Update X_Index[i] DAG parameter with X_Index DAG register    -   b) Update Y_Index[i] DAG parameter with Y_Index DAG register    -   14) Push a Service Request for Port i onto the PTP_DMA_Queue if        one is not already pending.

XMC Modes

In a preferred embodiment the XMC operates in eight basic modes. Theseinclude the following:

Basic Mode—Provides unrestricted reading of and writing to a datastructure. A write occurs when there is data in the temporary buffer andold data overwritten. A read occurs after an explicit read request hasbeen received and there is available space in the input buffer consumingnode. It does not consume data.

High-Speed-Write Mode—Similar to Basic Mode with the exception that readrequests are not supported, thereby achieving higher throughput inwriting to memory.

Finite-Sink Mode—Provides finite sink for data. A write occurs whenthere is data in the temporary buffer and available space in the mainbuffer. Writing stops when the main buffer is full.

Auto-Source Mode—Provides an infinite source of data. A read occursautomatically when there is available space in the input buffer of theconsuming node. Read Requests are not used.

Buffer Mode—Implements a buffer/FIFO. Writes fill the main buffer whilereads drain the main buffer. A write occurs when there is data in thetemporary buffer and available space in the main buffer. A read occurswhen there is sufficient data in the main buffer and available space inthe consuming node's input buffer.

Y-Wrap Mode—Permits a write to memory to end in the middle of adouble-word for the case when Record_Size is either byte or (16-bit)word.

Burst Mode—A special high-throughput mode for reading and writing 2-Dblocks of bytes. Similar to Y-Wrap Mode in that writes to memory can endin the middle of a double-word.

Burst-Write Mode—Identical to Burst Mode except that—likeHigh-Speed-Write Mode—read requests are not permitted. Achieves higherthroughput than Burst Mode in writing to memory.

Basic Mode

Basic Mode supports writing to and reading from memory with norestrictions on Port_Type, DAG parameters or the use of PTP controlwords. Reads are initiated either by a read request when Port_Type isPTP, PTP_Packet_Mode or RTI or by poking a 1 into DMA_Go when Port_Typeis DMA.

Table II lists the Control and Status Bit parameters that define BasicMode.

TABLE II Settings for Basic Mode Parameter Description Auto_Read 0: Portdoes not support automatic reads Buffer_Read 0: Consumer_Count notchecked in auto read Buffer_Write 0: New data overwrites old data inmemory Update_Index 1: Update DAG_X_Index and DAG_Y_Index after each DAGuse New_MIN_Word_On_YWrap 0: Ignore DAG_Y_Index wrap whenunpacking/packing MIN words High_Speed_Write 0: Normal mode; The porthandles all incoming words Burst 0: Normal DAG-addressing modeRandom_Access 0: Normal DAG addressing when performing read request

Where:

-   -   1. The compound condition (ACK_Count>=0 AND Producer_Count<0)        triggers the processing of words in the temporary buffer.        ACK_Count≧0 indicates that there are words in the temporary        buffer. Producer_Count<0 indicates that there is space available        in the consumer's input buffer in the event that a read request        is encountered.    -   2. Once processing begins, it continues until either a read        request is encountered (and processed) or the entire contents of        the temporary buffer—as indicated by ACK_Count when processing        begins—has been dispatched.    -   3. Data words from the temporary buffer are unpacked from right        to left^(†) and the records written to main-memory under DAG        direction. There is no flow control between the temporary buffer        and main memory and so new data may overwrite old.    -   4. When a control word without a read is encountered, the        indicated update is performed.    -   5. When a read request is encountered, the indicated update is        performed and Read_Count records are then read from main memory        under DAG direction, packed from right to left into double-words        and sent to the consumer node.    -   6. Upon completion of processing:        -   a) ACK_Count is decremented by 4× the total number of            words—both data and control—removed from the temporary            buffer        -   b) Consumer_Count is incremented by 4× the total number of            data words written to main memory        -   c) A Backward Acknowledgement is sent to Data Producer with            an value equal to minus 4× the total number of data words—if            any—written to main memory        -   d) A Backward Acknowledgement is sent to Control Producer            with an value equal to minus 4× the total number of control            words—if any—that are processed        -   e) If a read request has been processed:            -   i. Producer_Count is incremented by 4× the number of                double-words sent to Consumer            -   ii. A Forward Acknowledgement is sent to Consumer with                an value equal to 4× the number of double-words sent to                Consumer        -   f) The port is placed back on the PTP/DMA service queue to            process any remaining words in the temporary buffer    -   7. When a port is restricted to just writing—for example, when        the port is a DMA sink—High-Speed-Write Mode is recommended due        to its higher performance and because it is does not require        Producer_Count<0 in order to process words from the temporary        buffer.

High-Speed-Write Mode

High-Speed-Write Mode is similar to Basic Mode with the exception thatread requests are not supported. This can allows advantages such as notrequiring that Producer_Count<0 before words are removed from thetemporary buffer is eliminated. Also, words can be removed from thetemporary buffer at a higher rate.

Table III lists the Control and Status Bit parameters that defineHigh-Speed-Write Mode.

TABLE III Parameters for High-Speed-Write Mode Parameter DescriptionAuto_Read 0: Port does not support automatic reads Buffer_Read 0:Consumer_Count not checked in auto read Buffer_Write 0: New dataoverwrites old data in memory Update_Index 1: Update DAG_X_Index andDAG_Y_Index after each DAG use New_MIN_Word_On_YWrap 0: IgnoreDAG_Y_Index wrap when unpacking/packing MIN words High_Speed_Write 1:High-speed mode; the port does not support read requests Burst 0: NormalDAG-addressing mode Random_Access 0: Normal DAG addressing whenperforming read request

Where:

-   -   1. ACK_Count 0, indicating that there are words in the temporary        buffer, triggers the processing of those words.    -   2. Once processing begins, the entire contents of the temporary        buffer—as indicated by ACK_Count when processing begins—is        processed.    -   3. Data words from the temporary buffer are unpacked from right        to left^(†) and the records written to main-memory under DAG        direction. There is no flow control between the temporary buffer        and main memory and so new data may overwrite old.    -   4. When a control word is encountered, the indicated update is        performed.    -   5. Upon completion of processing:        -   a) ACK_Count is decremented by 4× the total number of            words—both data and control—removed from the temporary            buffer        -   b) Consumer_Count is incremented by 4× the total number of            data words written to main memory        -   c) A Backward Acknowledgement is sent to Data Producer with            a value equal to minus 4× the total number of data words—if            any—written to main memory        -   d) A Backward Acknowledgement is sent to Control Producer            with a value equal to minus 4× the total number of control            words—if any—that are processed    -   6. High-Speed-Write Mode is the recommended mode when a port is        a DMA sink.

Finite-Sink Mode

Finite-Sink mode allows data to be written to memory and preserved frombeing overwritten by subsequent data. This is useful, for example, forstoring statistics data, an error log, etc. Table IV lists the Controland Status Bit parameters that define Finite-Sink Mode.

TABLE IV Parameters for Finite-Sink Mode Parameter Description Auto_Read0: Port does not support automatic reads Buffer_Read 0: Consumer_Countnot checked in auto read Buffer_Write 1: No writes to main-memory bufferwhen full Update_Index 1: Update DAG_X_Index and DAG_Y_Index after eachDAG use New_MIN_Word_On_YWrap 0: Ignore DAG_Y_Index wrap whenunpacking/packing MIN words High_Speed_Write 1: High-speed mode; Portdoes not support read requests Burst 0: Normal DAG-addressing modeRandom_Access 0: Normal DAG addressing when performing read request

Where:

-   -   1. The compound condition (ACK_Count>=0 AND        Consumer_Count+Buffer_Full_Offset<0) triggers the processing of        words in the temporary buffer. ACK_Count≧0 indicates that there        are words in the temporary buffer.        Consumer_Count+Buffer_Full_Offset<0 indicates that there is at        least a temporary-buffer's worth of available space in the        main-memory buffer.    -   2. Once processing begins, the entire contents of the temporary        buffer—as indicated by ACK_Count when processing begins—is        processed.    -   3. Data words from the temporary buffer are unpacked from right        to left^(†) and the records written to main-memory under DAG        direction. There is flow control between the temporary buffer        and main memory and so new data does not overwrite old.    -   4. When a control word is encountered, the indicated update is        performed.    -   5. Upon completion of processing:        -   a) ACK_Count is decremented by 4× the total number of            words—both data and control—removed from the temporary            buffer        -   b) Consumer_Count is incremented by 4× the total number of            data words written to main memory        -   c) A Backward Acknowledgement is sent to Data Producer with            a value equal to minus 4× the total number of data words—if            any—written to main memory        -   d) A Backward Acknowledgement is sent to Control Producer            with a value equal to minus 4× the total number of control            words—if any—that are processed    -   6. Once Consumer_Count+Buffer_Full_Offset≧0, all processing of        words from the temporary buffer stops and any remaining words in        the temporary buffer remain there.

Auto-Source Mode

An application may need to make use of tables of constants. For example,wave tables, pseudo-random data, etc., are typically written at systeminitialization and accessed in a continuous stream during real-timeoperation. Auto-Source Mode provides a means for accessing such data.Table V lists the Control and Status Bit parameters that defineAuto-Source Mode.

TABLE V Parameters for Auto-Source Mode Parameter Description Auto_Read1: Producer/Consumer counts can automatically trigger a read Buffer_Read0: Consumer_Count not checked in auto read Buffer_Write 0: New dataoverwrites old data in memory Update_Index 1: Update DAG_X_Index andDAG_Y_Index after each DAG use New_MIN_Word_On_YWrap 0: IgnoreDAG_Y_Index wrap when unpacking/packing MIN words High_Speed_Write 1:High-speed mode; The port does not support read requests Burst 0: NormalDAG-addressing mode Random_Access 0: Normal DAG addressing whenperforming read request

Where:

-   -   1. Whenever Producer_Count<0, Read_Count records are read from        main memory under DAG direction, packed from right to left^(†)        into double-words and sent to Consumer. After each auto read:        -   a) Producer_Count is incremented by 4× the number of            double-words sent to Consumer        -   b) A Forward Acknowledgement is sent to Consumer with a            value equal to 4× the number of double-words sent to            Consumer    -   2. ACK_Count≧0, indicating that there are words in the temporary        buffer, triggers the processing of those words.    -   3. Once processing begins, the entire contents of the temporary        buffer—as indicated by ACK_Count when processing begins—is        processed.    -   4. Data words from the temporary buffer are unpacked from right        to left and the records written to main-memory under DAG        direction. There is no flow control between the temporary buffer        and main memory and so new data may overwrite old.    -   5. When a control word is encountered, the indicated update is        performed.    -   6. Upon completion of processing:        -   a) ACK_Count is decremented by 4× the total number of            words—both data and control—removed from the temporary            buffer        -   b) Consumer_Count is incremented by 4× the total number of            data words written to main memory        -   c) A Backward Acknowledgement is sent to Data Producer with            a value equal to minus 4× the total number of data words—if            any—written to main memory        -   d) A Backward Acknowledgement is sent to Control Producer            with a value equal to minus 4× the total number of control            words—if any—that are processed.

Buffer Mode

In a preferred embodiment, a port in Buffer Mode implements afirst-in-first-out queue. A delay line—a queue in which the amount ofdata in the queue remains above a threshold—is a form of FIFO and canalso be implemented in Buffer Mode. Table VI lists the Control andStatus Bit parameters that define Buffer Mode.

TABLE VI Parameters for Buffer Mode Parameter Description Auto_Read 1:Producer/Consumer counts can automatically trigger a read Buffer_Read 1:Consumer_Count >= 0 for auto read Buffer_Write 1: No writes tomain-memory buffer when full Update_Index 1: Update DAG_X_Index andDAG_Y_Index after each DAG use New_MIN_Word_On_YWrap 0: IgnoreDAG_Y_Index wrap when unpacking/packing MIN words High_Speed_Write 1:High-speed mode; The port does not support read requests Burst 0: NormalDAG-addressing mode Random_Access 0: Normal DAG addressing whenperforming read request

Where:

-   -   1. The compound condition (ACK_Count >=0 AND        Consumer_Count+Buffer_Full_Offset<0) triggers the processing of        words in the temporary buffer. ACK_Count≧0 indicates that there        are words in the temporary buffer.        Consumer_Count+Buffer_Full_Offset<0 indicates that there is at        least a temporary-buffer's worth of available space in the        main-memory buffer.    -   2. Once processing begins, the entire contents of the temporary        buffer—as indicated by ACK_Count when processing begins—is        processed.    -   3. Data words from the temporary buffer are unpacked from right        to left^(†) and the records written to main-memory under DAG        direction. There is flow control between the temporary buffer        and main memory and so new data does not overwrite old.    -   4. When a control word is encountered, the indicated update is        performed.    -   5. When processing of words from the temporary buffer is        completed:        -   a) ACK_Count is decremented by 4× the total number of            words—both data and control—removed from the temporary            buffer        -   b) Consumer_Count is incremented by 4× the total number of            data words written to main memory        -   c) A Backward Acknowledgement is sent to Data Producer with            a value equal to minus 4× the total number of data words—if            any—written to main memory        -   d) A Backward Acknowledgement is sent to Control Producer            with a value equal to minus 4× the total number of control            words—if any—that are processed    -   7. The compound condition (Consumer_Count>=0 AND        Producer_Count<0) triggers an auto read in which Read_Count        records are read from main memory under DAG direction, packed        from right to left into double-words and sent to Consumer. After        each auto read:        -   a) Consumer_Count is decremented by 4× the number of            double-words removed from the main memory buffer        -   b) Producer_Count is incremented by 4× the number of            double-words sent to Consumer        -   c) A Forward Acknowledgement is sent to Consumer with a            value equal to 4× the number of double-words sent to            Consumer    -   8. The initial value of Consumer_Count sets a threshold on the        amount of data in the main-memory buffer necessary for an auto        read to occur. If the initial value of Consumer_Count is −n,        then n is the amount of data, expressed in bytes, necessary for        an auto read to occur.    -   9. The minimum number of double-words in the main-memory        buffer—after an initial transient phase when the buffer is        filling up—is: −((Initial value of Consumer_Count)/4+Read_Count)        double-words    -   10. For example, if the initial value of Consumer_Count is        −40,000 (bytes) and Read_Count is 100 (double-words) then an        auto read occurs only after 10,000 double-words (40,000 bytes)        have been written into the main-memory buffer. When an auto read        does occur, 100 double-words are removed from the buffer and        Consumer_Count is decremented by 400 (bytes). Since there must        have been at least 10,000 double-words in buffer before the auto        read occurred, there must be at least 10,000−100=9,900        double-words in the buffer after the auto read occurred. This        number, 9,900, is the minimum number of double-words that can be        in the main-memory buffer after the initial transient when the        buffer is filling up.

Y-Wrap Mode

Y-Wrap Mode, along with Burst Mode and Burst-Write Mode, permit a writeto memory to end in the middle of a double-word. Y-Wrap Mode can beused, for example, when writing a block of pixels (bytes) by rows into atwo-dimensional frame buffer. In this case, the Y Wrap occurs when thelast pixel of the block is written into memory. Any remaining bytes inthe last data word are discarded and the next block of pixels beginswith a new data word from the MIN. Table VII lists the Control andStatus Bit parameters that define Y-Wrap Mode.

TABLE VII Parameters for Y-Wrap Mode Parameter Description Auto_Read 0:Port does not support automatic reads Buffer_Read 0: Consumer_Count notchecked in auto read Buffer_Write 0: New data overwrites old data inmemory Update_Index 1: Update DAG_X_Index and DAG_Y_Index after each DAGuse New_MIN_Word_On_YWrap 1: Start unpacking/packing new MIN word whenDAG_Y_Index wraps High_Speed_Write 1: High-speed mode; The port does notsupport read requests Burst 0: Normal DAG-addressing mode Random_Access0: Normal DAG addressing when performing read request

Where:

-   -   1. ACK_Count≧0, indicating that there are words in the temporary        buffer, triggers the processing of those words.    -   2. Once processing begins, the entire contents of the temporary        buffer—as indicated by ACK_Count when processing begins—is        processed.    -   3. Data words from the temporary buffer are unpacked from right        to left^(†) and the records written to main-memory under DAG        direction. Upon a Y Wrap (DAG_Y_Index wraps around), writing is        immediately terminated and any remaining records in the data        (double-) word are discarded.    -   4. There is no flow control between the temporary buffer and        main memory and so new data may overwrite old.    -   5. When a control word is encountered in the temporary buffer,        the indicated update is performed.    -   6. When processing of words from the temporary buffer is        completed:        -   a) ACK_Count is decremented by 4× the total number of            words—both data and control—removed from the temporary            buffer        -   b) Consumer_Count is incremented by 4× the total number of            data words written to main memory        -   c) A Backward Acknowledgement is sent to Data Producer with            a value equal to minus 4× the total number of data words—if            any—written to main memory        -   d) A Backward Acknowledgement is sent to Control Producer            with a value equal to minus 4× the total number of control            words—if any—that are processed    -   7. Example: Suppose Record_Size=byte, DAG_Address_Mode=2-D and        the DAG is configured to address a 9×9 block of records. When        the 21^(st) double-word of an incoming block is encountered,        only the right-most byte—which is the 81^(st) byte of the        block—is written to memory because DAG_Y_Index wraps immediately        after that byte is written. The remaining three bytes in the        double-word are discarded and writing of the next block begins        with a new double-word from the MIN. ^(†) Records are packed and        unpacked from right to left because the XMC is little endian.

Burst Mode

Burst Mode can be useful in imaging or video applications (e.g., MPEG4,HDTV, etc.) that have high bandwidth/throughput requirements. In apreferred embodiment, Burst Mode makes use of the Double Data Rate (DDR)feature of DDR DRAM. Other applications can use other types of memoryand need not use the DDR feature. Burst Mode allows blocks of pixels tobe either written to or read from memory at very high rates. Burst Modeterminates writing (and reading) of a double-word on an X-Wrap. Thisdifference means that each line, not just each block, begins with a newdouble-word. Table VIII lists the Control and Status Bit parameters thatdefine Burst Mode.

TABLE VIII Parameters for Burst Mode Parameter Description Auto_Read 0:Port does not support automatic reads Buffer_Read 0: Consumer_Count notchecked in auto read Buffer_Write 0: New data overwrites old data inmemory Update_Index 1: Update DAG_X_Index and DAG_Y_Index after each DAGuse New_MIN_Word_On_YWrap 0: Ignore DAG_Y_Index wrap whenunpacking/packing MIN words High_Speed_Write 0: Normal mode; The porthandles all incoming words Burst 1: High-throughput mode for accessingcontiguous blocks of 2-D data Random_Access 0: Normal DAG addressingwhen performing read request

Where:

-   -   1. The compound condition (ACK_Count>=0 AND Producer_Count<0)        triggers the processing of words in the temporary buffer.        ACK_Count≧0 indicates that there are words in the temporary        buffer. Producer_Count<0 indicates that there is space available        in the consumer's input buffer in the event that a read request        is encountered.    -   2. Once processing begins, it continues until either a read        request is encountered (and processed) or the entire contents of        the temporary buffer—as indicated by ACK_Count when processing        begins—has been dispatched.    -   3. Data words from the temporary buffer are unpacked from right        to left^(†) and the records written to main-memory under DAG        direction. Upon an X Wrap (DAG_X_Index wraps around), writing is        immediately terminated and any remaining records in the data        (double-) word are discarded.    -   4. There is no flow control between the temporary buffer and        main memory and so new data may overwrite old.    -   5. When a control word without a read is encountered, the        indicated update is performed.    -   6. When a read request is encountered, the indicated update is        performed and Read_Count records are then read from main memory        under DAG direction, packed from right to left into double-words        and sent to the consumer node.    -   7. Upon completion of processing:        -   a) ACK_Count is decremented by 4× the total number of            words—both data and control—removed from the temporary            buffer        -   b) Consumer_Count is incremented by 4× the total number of            data words written to main memory        -   c) A Backward Acknowledgement is sent to Data Producer with            a value equal to minus 4× the total number of data words—if            any—written to main memory        -   d) A Backward Acknowledgement is sent to Control Producer            with a value equal to minus 4× the total number of control            words—if any—that are processed        -   e) If a read request has been processed:            -   i. Producer_Count is incremented by 4× the number of                double-words sent to Consumer            -   ii. A Forward Acknowledgement is sent to Consumer with a                value equal to 4× the number of double-words sent to                Consumer        -   f) The port is placed back on the PTP/DMA service queue to            process any remaining words in the temporary buffer    -   8. In the restriction above—The Data Producer ACKs in multiples        of 4×ceil(DAG_X_Limit/4)−ceil(DAG_X_Limit/4) is the number of        double-words needed for each line in a block of pixels.        4×ceil(DAG_X_Limit/4) is that number converted to bytes. The        restriction guarantees that ACK_Count will always reflect an        integral number of lines in the temporary buffer and the port        will therefore always write an integral number of lines to        memory.    -   9. The restriction above—Read_Count is an integer multiple of        DAG_X_Limit—guarantees that the port will always read an        integral number of lines from memory.    -   10. Write example: Suppose Record_Size=byte,        DAG_Address_Mode=2-D and the DAG is configured to address a 9×9        block of records. When the 3^(rd), 6^(th), 9^(th), 12^(th),        15^(th), 18^(th), 21^(st), 24^(th) or 27^(th) double-word of an        incoming block is encountered, only the right-most byte—which is        the 9^(th) byte of a line—is written to memory because        DAG_X_Index wraps immediately after that byte is written. The        remaining three bytes in the double-word are discarded and        writing of the next line in the block begins with a new        double-word from the MIN. Notice that this incoming 9×9 block of        pixels requires 27 double-words in Burst Mode, but only 21        double-words in Y-Wrap Mode.    -   11. Read example: Suppose Record_Size=byte,        DAG_Address_Mode=2-D, the DAG is configured to address a 9×9        block of records and Read_Count=81. Now suppose that a read        request is encountered in the temporary buffer. The port will        read bytes from memory and pack them into outgoing double-words.        But when the port gets to the 3^(rd), 6^(th), 9^(th), 12^(th),        16^(th), 18^(th), 21^(st), 24^(th) or 27^(th) double-word, it        will place only a single byte—the 9^(th) byte of a line—in the        double-word (in the right-most position) because DAG_X_Index        wraps immediately after that byte is read. The next byte—the        first byte of the next line—goes into a new double-word. Notice        that this outgoing 9×9 block of pixels requires 27 double-words        in Burst Mode, but only 21 double-words in Basic Mode. ^(†)        Records are packed and unpacked from right to left because the        XMC is little endian.

Burst-Write Mode

Burst-Write Mode allows higher throughput than Burst Mode by notsupporting read requests and by not requiring Producer_Count<0 in orderto begin processing words from the temporary buffer. Table IX lists theControl and Status Bit parameters that define Burst-Write Mode.

TABLE IX Parameters for Burst-Write Mode Parameter Description Auto_Read0: Port does not support automatic reads Buffer_Read 0: Consumer_Countnot checked in auto read Buffer_Write 0: New data overwrites old data inmemory Update_Index 1: Update DAG_X_Index and DAG_Y_Index after each DAGuse New_MIN_Word_On_YWrap 0: Ignore DAG_Y_Index wrap whenunpacking/packing MIN words High_Speed_Write 1: High-speed mode; Theport does not support read requests Burst 1: High-throughput mode foraccessing contiguous blocks of 2-D data Random_Access 0: Normal DAGaddressing when performing read request

Where:

-   -   1. ACK_Count 0, indicating that there are words in the temporary        buffer, triggers the processing of those words.    -   2. Once processing begins, the entire contents of the temporary        buffer—as indicated by ACK_Count when processing begins—is        processed.    -   3. Data words from the temporary buffer are unpacked from right        to left^(†) and the records written to main-memory under DAG        direction. Upon an X Wrap (DAG_X_Index wraps around), writing is        immediately terminated and any remaining records in the data        (double-) word are discarded.    -   4. There is no flow control between the temporary buffer and        main memory and so new data may overwrite old.    -   5. When a control word is encountered in the temporary buffer,        the indicated update is performed.    -   6. Upon completion of processing:        -   a) ACK_Count is decremented by 4× the total number of            words—both data and control—removed from the temporary            buffer        -   b) Consumer_Count is incremented by 4× the total number of            data words written to main memory        -   c) A Backward Acknowledgement is sent to Data Producer with            a value equal to minus 4× the total number of data words—if            any—written to main memory        -   d) A Backward Acknowledgement is sent to Control Producer            with a value equal to minus 4× the total number of control            words—if any—that are processed    -   7. In the restriction above—The Data Producer ACKs in multiples        of 4×ceil(DAG_X_Limit/4)−ceil(DAG_X_Limit/4) is the number of        double-words needed for each line in a block of pixels.        4×ceil(DAG_X_Limit/4) is that number converted to bytes. The        restriction guarantees that ACK_Count will always reflect an        integral number of lines in the temporary buffer and the port        will therefore always write an integral number of lines to        memory.    -   8. Write Example: Suppose Record_Size=byte, DAG_Address_Mode=2-D        and the DAG is configured to address a 9×9 block of records.        When the 3^(rd), 6^(th), 9^(th), 12^(th), 15^(th), 18^(th),        21^(st), 24^(th) or 27^(th) double-word of an incoming block is        encountered, only the right-most byte—which is the 9^(th) byte        of a line—is written to memory because DAG_X_Index wraps        immediately after that byte is written. The remaining three        bytes in the double-word are discarded and writing of the next        line in the block begins with a new double-word from the MIN.        Notice that this incoming 9×9 block of pixels requires 27        double-words in Burst Mode, but only 21 double-words in Y-Wrap        Mode.

Applications

The features of the XMC can be used to advantage in different waysdepending on a specific application. For example, in a “data-sinking”application it is sometimes necessary to store information about systemperformance (e.g., statistics or an error log) in memory. The data mayhave to be stored in real time and prevented from being overwritten bysubsequent data. An XMC port configured in Finite-Sink Mode can providethat capability. The parameter settings for this mode are shown in TableX, below.

Real-time data are written into a buffer in memory until the bufferbecomes full whereupon writing ceases. The data can be read at any timevia a read request.

TABLE X Data-Sinking Application Read/Write Port i PTP/DMA_ModeFinite-Sink Mode Record_Size double-word (32 bits) Read_Count read-blocksize (records) Addressing_Mode 1-D DAG_Origin start of bufferDAG_X_Index read pointer (initialized to 0) DAG_X_Stride 4 (bytes)DAG_X_Limit buffer size (bytes) DAG_Y_Index write pointer (initializedto 0) DAG_Y_Stride 4 (bytes) DAG_Y_Limit buffer size (bytes)

Another application is known as “data sourcing”. Applications sometimesrequire a large or unbounded stream of fixed data—pseudo-random data ora wave table, for example—during real-time operation.

To provide the stream an XMC port can be configured in Auto-Source Modeaccessing a circular buffer in memory containing the fixed dataconfigured according to Table XI. The fixed data—which is typicallywritten into the buffer at system initialization—can be suppliedautomatically to the consumer node, the flow being governed by normalPTP flow control using Forwards and Backwards ACKs. Because the bufferis circular and Buffer_Read is turned off, the port provides an infinitesource of data.

TABLE XI Data-Sourcing Application Read/Write Port i PTP/DMA_ModeAuto-Source Mode Record_Size double-word (32 bits) Read_Count read-blocksize (records) Addressing_Mode 1-D DAG_Origin start of bufferDAG_X_Index read pointer (initialized to 0) DAG_X_Stride 4 (bytes)DAG_X_Limit buffer size (bytes) DAG_Y_Index write pointer (initializedto 0) DAG_Y_Stride 4 (bytes) DAG_Y_Limit buffer size (bytes)

Another type of application may require implementation of “delay lines.”For example, digital audio broadcast, personal video recorders, modelingof acoustics, etc., types of applications can require a signal to bedelayed by a number of samples. This requirement usually means thatthere will always be a certain minimum number of samples in the delayline once the line reaches steady-state operation (once the number ofsamples in the delay line reaches a threshold).

A delay line is implemented using a single port configured in BufferMode with Record_Size set to double-word as shown in Table XII. Thecircular buffer in main memory is accessed by DAG_X_Index for readingand DAG_Y_Index for writing. The initial value of Consumer_Countdetermines the length/size of the delay line: it is initialized to minusthe size of the delay, converted to bytes.

For example, to implement a delay line of 1,000,000 double-words, abuffer of at least 4,000,000 bytes is allocated in memory andConsumer_Count is initialized to −4,000,000 as illustrated in Table.Because of the initial value of Consumer_Count, no output appears untilat least 1,000,000 double-words have been written into the buffer andConsumer_Count has been incremented by a cumulative value of at least+4,000,000 (by Forward ACKs from the Data Producer). After thatthreshold has been reached and Consumer_Count has been drivennon-negative, an auto read occurs.

In this example, the consumer node expects to get data from the delayline in blocks of 100 double-words, and so Read_Count is set to 100(records). Upon an auto read, 100 double-words are removed from thebuffer and sent to the Consumer (assuming Producer. Count<0).Consumer_Count is then decremented by 400 (bytes). If the new value ofConsumer_Count is still non-negative, then another auto read occurs andthe cycle is repeated. If the new value of Consumer_Count is negative,then reading is inhibited until additional double-words are written intothe buffer and Consumer_Count is again driven non-negative.

In summary, once the number of samples in the delay line reaches atleast 1,000,000 and Consumer_Count becomes non-negative, Consumer_Countnever drops below −400 and the number of double-words in the delay linenever drops below 999,900.

TABLE XII Delay-Line Application Read/Write Port i PTP/DMA_Mode BufferMode Record_Size double-word (32 bits) Read_Count 100 (records)Consumer_Count −4,000,000 (initial value in bytes) Addressing_Mode 1-DDAG_Origin start of buffer DAG_X_Index read pointer (initialized to 0)DAG_X_Stride 4 (bytes) DAG_X_Limit ≧4,000,000 (buffer size in bytes)DAG_Y_Index write pointer (initialized to 0) DAG_Y_Stride 4 (bytes)DAG_Y_Limit ≧4,000,000 (buffer size in bytes)

Another type of application may require “data reordering” in which theelements in a block of data need to be reordered. Table XIII illustratesan application—sometimes called a corner-turner or corner-bender—thatinterchanges the rows and columns of a two-dimensional block of data.The application example uses two XMC ports—Write Port i and Read Portj—both accessing the same two-dimensional buffer in memory.

For example, bytes can be written four at a time to memory by rows(lines) using Port i, which has the DAG, configured in 1-D mode. (2-Dmode could have been used, but 1-D is simpler and generates the samesequence of addresses.) When the Data Producer receives acknowledgementfrom the XMC that all data has been written to main memory, it signalsthe Consumer to begin reading. The Consumer sends a backwards ACK to XMCPort j thereby driving Producer_Count negative and enabling a read.

Bytes are read from memory by columns using Port j with the DAG in 2-Dmode. But because reading is by columns and not rows, the usual roles ofDAG_X_Index and DAG_Y_Index are reversed. DAG_X_Index now indexessuccessive bytes in a column, and DAG_Y_Index now indexes successivecolumns in the 2-D block. More precisely,

DAG_X_Index=R X line-length

DAG_Y_Index=C

where R and C are the row and column, respectively, of a byte in the 2-Dblock. After each byte is read, DAG_X_Index is incremented byline-length thereby accessing the next byte in the column. After thelast byte in the column is read, DAG_X_Index reaches L X line-length,where L is the number of lines (rows) in the 2-D block. But L Xline-length=buffer-size=DAG_X_Limit and therefore DAG_X_Index wrapsaround to 0 and DAG_Y_Index is incremented by 1. The cycle is repeatedfor each column until DAG_Y_Index=line−length=DAG_Y_Limit, theindication that the entire block has been read. When the Consumerreceives the entire block of data, it signals the Data Producer to beginwriting once again.

TABLE XIII Data-Reordering Application Write Port i Read Port jPTP/DMA_Mode High-Speed-Write Mode Basic Mode Buffer_Read 0 0Buffer_Write 0 0 Record_Size double-word byte Read_Count — read-blocksize (records) Addressing_Mode 1-D 2-D DAG_Origin start of buffer startof buffer DAG_X_Index — 0 (initial value) DAG_X_Stride — line length(bytes) DAG_X_Limit — buffer size (bytes) DAG_Y_Index write pointer 0(initial value) (initialized to 0) DAG_Y_Stride 4 (bytes) 1 (byte)DAG_Y_Limit buffer size (bytes) line length (bytes)

The XMC allows interlacing, or multiplexing, of multiple data streamsinto a single data stream. In Table XIV two streams arriving on XMCPorts i and j are combined in memory and then read from memory via XMCPort k.

In a preferred embodiment interlacing of the two streams is accomplishedby writing bytes arriving on Port i to even byte addresses in themain-memory buffer, and writing bytes arriving on Port j to odd byteaddresses. (Note that when DAG_Y_Index for Port i wraps around itreturns to 0, but when DAG_Y_Index for Port j wraps around it returns to1.)

Synchronizing of writing and reading is accomplished using adouble-buffering scheme in which the two Data Producers write into onehalf of the main-memory buffer while the Consumer reads the other half.To make the scheme work, each Data Producer signals the Consumer when itreceives acknowledgement from the XMC that buffer-size/4 bytes have beenwritten into the main-memory buffer. When the Consumer receives a signalfrom each Data Producer, it sends a backwards ACK to XMC Port k therebydriving Producer_Count negative and enabling a read of the interlaceddata. When the Consumer receives buffer-size/2 bytes of interlaced data,it signals each Data Producer that they are permitted to write into thebuffer half just read.

TABLE XIV Data-Interlacing Application Write Port i Write Port j ReadPort k PTP/DMA_Mode Y-Wrap Mode Y-Wrap Mode Basic Mode Record_Size bytebyte word (16 bits) Read_Count — — buffer size/4 (records)Addressing_Mode 1-D 1-D 1-D DAG_Origin start of buffer start of buffer +1 start of buffer DAG_X_Index — — 0 (initial value) DAG_X_Stride — — 2(bytes) DAG_X_Limit — — buffer size (bytes) DAG_Y_Index 0 (initialvalue) 0 (initial value) — DAG_Y_Stride 2 (bytes) 2 (bytes) —DAG_Y_Limit buffer size buffer size (bytes) — (bytes)

Data de-interlacing (de-multiplexing) is accomplished whereby instead ofmerging two data streams into one, one data stream is separated intotwo.

Table XV illustrates an application that reverses the interlacingoperation described in the preceding section. The input data streamarrives on XMC Port i and the two de-interlaced streams exit the XMC viaPorts j and k. De-interlacing is accomplished by reading even bytes inthe main-memory buffer using Port j and odd bytes using Port k. (Notethat when DAG_X_Index for Port j wraps around it returns to 0, but whenDAG_X_Index for Port j wraps around it returns to 1.)

Synchronizing of writing and reading is accomplished using adouble-buffering scheme in which the Data Producer writes into one halfof the main-memory buffer while the two Consumers read the other half.To make the scheme work, the Data Producer notifies the Consumers whenit receives acknowledgement from the XMC that buffer-size/2 bytes havebeen written into the buffer. When the two Consumers receive the signal,they each send a backwards ACK to their XMC read port thereby drivingProducer_Count negative and enabling a read of the de-interlaced data.When each Consumer receives buffer-size/4 bytes of data, it notifies theData Producer that reading of the half buffer has been completed. TheData Producer waits until it receives notification from both Consumersbefore it begins writing into the just-vacated half buffer.

TABLE XV Data De-Interlacing Application Write Port i Read Port j ReadPort k PTP/DMA_Mode Y-Wrap Mode Basic Mode Basic Mode Record_Size word(16 bits) byte byte Read_Count — buffer size/4 buffer size/4 (records)(records) Addressing_Mode 1-D 1-D 1-D DAG_Origin start of buffer startof buffer start of buffer + 1 DAG_X_Index — 0 (initial value) 0 (initialvalue) DAG_X_Stride — 2 (bytes) 2 (bytes) DAG_X_Limit — buffer sizebuffer size (bytes) (bytes) DAG_Y_Index 0 (initial value) — —DAG_Y_Stride 2 (bytes) — — DAG_Y_Limit buffer size — — (bytes)

Many video compression algorithms (e.g., MPEG) require reading numerousrectangular blocks of pixels (bytes) from a frame buffer. Table XVIillustrates an application in which data are written sequentially into aframe buffer via XMC Port i and in which rectangular blocks within theframe are read via XMC Port j.

A Data Producer for Port i writes data into the frame bufferline-by-line via Port i, and when it receives acknowledgement from theXMC that the entire frame has been written to memory, it notifies theControl Producer for Port j.

A Control Producer for Port j then sends a separate read request (seeSection Error! Reference source not found.) to Port j for each block ofpixels to be read, the parameter-update value in the request being usedto update DAG_Origin. This newly updated value for DAG_Origin determinesthe location of the block to be read. The remaining DAG parametersdetermine the size of the block to be read. Table illustrates theparameter settings for a 9×9 block of pixels (bytes).

TABLE XVI Frame-Buffer Application Write Port i Read Port j PTP/DMA_ModeHigh-Speed-Write Mode Basic Mode or Burst Mode Record_Size double-word(32 bits) byte Read_Count — 81 (records) Addressing_Mode 1-D 2-DDAG_Origin start of buffer updated via read request DAG_X_Index — 0(initial value) DAG_X_Stride — 1 (byte) DAG_X_Limit — 9 (bytes)DAG_Y_Index 0 (initial value) 0 (initial value) DAG_Y_Stride 4 (bytes)line length (bytes) DAG_Y_Limit buffer size (bytes) 9 × line length(bytes)

The XMC provides a scheme employing indirect addressing. In indirectaddressing data is accessed in two steps: (1) an address (pointer) isused to access a second address (pointer) and (2) this second address isused in turn to access user data. The XMC implements indirect addressingvia two tables, Table A and Table B, both residing in main memory asshown in Table XVII. Table A—which is accessed via XMC Port j—containspointers into Table B. Table B—which is accessed via XMC Port k—containsuser data.

Port j is configured in Auto-Source Mode and the entries in Table 1 areread automatically, in order, and sent via PTP control words from XMCPort j to XMC Port k. (Note the Consumer_ID and Consumer Port for Portj.) Normal PTP flow control between Port j and Port k guarantees thatthe input buffer on Port k never overflows.

Each entry in Table A has a format where bit 31 (TableAEntry[31]) is setto 1, bits 30-28 (TableAEntry[30:28]) are set to 001 and bits 27-0 areused for the new DAG_X_Index value. TableAEntry[30:28]=001 indicatesthat DAG_X_Index[k] is to be updated with the value inTableAEntry[27:0]. TableAEntry[31]=1 indicates that the update is to beimmediately followed by a read of Table B.

Port k responds to read requests from Port j as it would from any othersource. It updates the appropriate DAG parameter—DAG_X_Index in thiscase—and then sends Read_Count records to the consumer of user data.Normal PTP flow control between XMC Port k and the data consumerguarantees that the data-consumer's input buffer never overflows.

TABLE XVII Indirect-Addressing Application Read Port j (Table A) ReadPort k (Table B) PTP/DMA_Mode Auto-Source Mode Basic Mode Consumer_IDXMC consumer of user data (Consumer_ID[0] = 1 indicating a control word)Consumer_Port K consumer port Record_Size double-word (32 bits) userdefined Record Format { 1, 001, Pointer[27:0] } user defined (Record[31]= 1 indicates a read request) (Record[30:28] = 001 indicates X_Indexupdate) Read_Count ½ size of the input typically 1 (record) buffer ofPort k Addressing_Mode 1-D 1-D DAG_Origin start of Table A start ofTable B DAG_X_Index 0 (initial value) updated via read request from Portj DAG_X_Stride 4 (bytes) — DAG_X_Limit size of Table 1 (bytes) —DAG_Y_Index — — DAG_Y_Stride — — DAG_Y_Limit — —

Although the invention has been described with respect to specificembodiments thereof, these embodiments are merely illustrative, and notrestrictive, of the invention. For example, although a PIN has beendescribed as a data transfer mechanism other embodiments can use anytype of network or interconnection scheme.

Any suitable programming language can be used to implement the routinesof the present invention including C, C++, Java, assembly language, etc.Different programming techniques can be employed such as procedural orobject oriented. The routines can execute on a single processing deviceor multiple processors. Although the steps, operations or computationsmay be presented in a specific order, this order may be changed indifferent embodiments. In some embodiments, multiple steps shown assequential in this specification can be performed at the same time. Thesequence of operations described herein can be interrupted, suspended,or otherwise controlled by another process, such as an operating system,kernel, etc. The routines can operate in an operating system environmentor as stand-alone routines occupying all, or a substantial part, of thesystem processing.

In the description herein, numerous specific details are provided, suchas examples of components and/or methods, to provide a thoroughunderstanding of embodiments of the present invention. One skilled inthe relevant art will recognize, however, that an embodiment of theinvention can be practiced without one or more of the specific details,or with other apparatus, systems, assemblies, methods, components,materials, parts, and/or the like. In other instances, well-knownstructures, materials, or operations are not specifically shown ordescribed in detail to avoid obscuring aspects of embodiments of thepresent invention.

A “computer-readable medium” for purposes of embodiments of the presentinvention may be any medium that can contain, store, communicate,propagate, or transport the program for use by or in connection with theinstruction execution system, apparatus, system or device. The computerreadable medium can be, by way of example only but not by limitation, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus, system, device, propagation medium, orcomputer memory.

A “processor” or “process” includes any human, hardware and/or softwaresystem, mechanism or component that processes data, signals or otherinformation. A processor can include a system with a general-purposecentral processing unit, multiple processing units, dedicated circuitryfor achieving functionality, or other systems. Processing need not belimited to a geographic location, or have temporal limitations. Forexample, a processor can perform its functions in “real time,”“offline,” in a “batch mode,” etc. Portions of processing can beperformed at different times and at different locations, by different(or the same) processing systems.

Reference throughout this specification to “one embodiment”, “anembodiment”, or “a specific embodiment” means that particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention and notnecessarily in all embodiments. Thus, respective appearances of thephrases “in one embodiment”, “in an embodiment”, or “in a specificembodiment” in various places throughout this specification are notnecessarily referring to the same embodiment. Furthermore, theparticular features, structures, or characteristics of any specificembodiment of the present invention may be combined in any suitablemanner with one or more other embodiments. It is to be understood thatother variations and modifications of the embodiments of the presentinvention described and illustrated herein are possible in light of theteachings herein and are to be considered as part of the spirit andscope of the present invention.

Embodiments of the invention may be implemented by using a programmedgeneral purpose digital computer, by using application specificintegrated circuits, programmable logic devices, field programmable gatearrays, optical, chemical, biological, quantum or nanoengineeredsystems, components and mechanisms may be used. In general, thefunctions of the present invention can be achieved by any means as isknown in the art. Distributed, or networked systems, components andcircuits can be used. Communication, or transfer, of data may be wired,wireless, or by any other means.

It will also be appreciated that one or more of the elements depicted inthe drawings/figures can also be implemented in a more separated orintegrated manner, or even removed or rendered as inoperable in certaincases, as is useful in accordance with a particular application. It isalso within the spirit and scope of the present invention to implement aprogram or code that can be stored in a machine-readable medium topermit a computer to perform any of the methods described above.

Additionally, any signal arrows in the drawings/Figures should beconsidered only as exemplary, and not limiting, unless otherwisespecifically noted. Furthermore, the term “or” as used herein isgenerally intended to mean “and/or” unless otherwise indicated.Combinations of components or steps will also be considered as beingnoted, where terminology is foreseen as rendering the ability toseparate or combine is unclear.

As used in the description herein and throughout the claims that follow,“a”, “an”, and “the” includes plural references unless the contextclearly dictates otherwise. Also, as used in the description herein andthroughout the claims that follow, the meaning of “in” includes “in” and“on” unless the context clearly dictates otherwise.

The foregoing description of illustrated embodiments of the presentinvention, including what is described in the Abstract, is not intendedto be exhaustive or to limit the invention to the precise formsdisclosed herein. While specific embodiments of, and examples for, theinvention are described herein for illustrative purposes only, variousequivalent modifications are possible within the spirit and scope of thepresent invention, as those skilled in the relevant art will recognizeand appreciate. As indicated, these modifications may be made to thepresent invention in light of the foregoing description of illustratedembodiments of the present invention and are to be included within thespirit and scope of the present invention.

Thus, while the present invention has been described herein withreference to particular embodiments thereof, a latitude of modification,various changes and substitutions are intended in the foregoingdisclosures, and it will be appreciated that in some instances somefeatures of embodiments of the invention will be employed without acorresponding use of other features without departing from the scope andspirit of the invention as set forth. Therefore, many modifications maybe made to adapt a particular situation or material to the essentialscope and spirit of the present invention. It is intended that theinvention not be limited to the particular terms used in followingclaims and/or to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include any and all embodiments and equivalents falling within thescope of the appended claims.

1-32. (canceled)
 33. A computing machine comprising: a memory; aplurality of computational nodes embodied in an integrated circuit andeach configured to make requests for memory accesses to the memory; anda memory controller configured to place the requests for memory accessesin a queue and allow accesses by the computational nodes to the memoryin an order established by the queue.